diff --git a/NEWS.md b/NEWS.md
index eea3134..5ef31bb 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,37 @@
 # uscogdata 0.1.0 (development)
 
+## `complete = TRUE`: absent cells, labelled with why they are absent
+
+* `cog_spending()` and `cog_revenue()` gain `complete`, defaulting to `FALSE`
+  (today's behaviour). With `complete = TRUE` the requested grid is filled
+  from the corpus's `code_set` table and every row carries a new
+  `value_source` column:
+
+  | `value_source` | meaning | `amt_nominal` |
+  |---|---|---|
+  | `reported` | the corpus carries this cell | as published |
+  | `census_zero` | dense-source year (≤ FY2011), cell absent — Census published `$0` | `0` |
+  | `not_reported` | sparse-source year (≥ FY2012), cell absent — unknown | `NA` |
+
+  The `NA` is deliberate and is the whole point: filling a modern absence
+  with `0` would invent data, which is precisely the error the corpus's
+  representation contract exists to prevent.
+* This restores information the reader lost when the corpus was sparsified
+  (`SB194`, cog_pipeline#64) — a wide-era query whose cells were all `$0`
+  had begun returning nothing at all — and improves on what came before it,
+  since the pre-sparsification corpus could not distinguish a published zero
+  from an unreported cell either.
+* The grid is scoped to each government's **own type**, so a county is never
+  filled with cells only a state can report.
+* Needs a corpus published from 2026-07-29 onward (when `representation` and
+  `code_set` began shipping); aborts with class
+  `uscogdata_representation_unavailable` otherwise. Gated on the manifest
+  listing those tables rather than on `schema_version`, which was never
+  bumped for the change. Not available with `recipe` or
+  `expenditure_concept = "total"` — neither draws its cells from `code_set`.
+* `provenance$completion` reports `applied`, `rows_filled`, and the per-year
+  `absence_means` rule; `cog_explain()` prints a "Completion" section.
+
 ## Corpus-wide series breaks now reach users (`corpus_break_refs`)
 
 * Four catalogued series breaks carry `fin_code = "ALL"` — caveats about the
diff --git a/R/complete.R b/R/complete.R
new file mode 100644
index 0000000..b2c6cfc
--- /dev/null
+++ b/R/complete.R
@@ -0,0 +1,148 @@
+# R/complete.R
+#
+# `complete = TRUE` on the money verbs. Fills the requested grid so that a
+# cell the corpus does not carry still appears, labelled with WHY it is
+# missing.
+#
+# The corpus stopped storing the wide era's explicit zeros
+# (cog_pipeline#64, series break SB194), which made absence ambiguous:
+#
+#   <= FY2011  dense_source   absent => Census published $0    (census_zero)
+#   >= FY2012  sparse_source  absent => not reported, unknown  (not_reported)
+#
+# Before sparsification a wide-era query whose cells were all $0 came back as
+# explicit $0 rows; afterwards it came back empty, with nothing to say which
+# of the two meanings applied. This restores that -- and improves on it,
+# because the pre-sparsification corpus could not distinguish the two either.
+#
+# `census_zero` fills carry `amt_nominal = 0`; `not_reported` fills carry NA.
+# That difference is the entire point: writing 0 into a modern absence would
+# invent data, which is the error the representation contract exists to stop.
+
+#' @noRd
+.abort_complete_unsupported <- function(reason, alternative) {
+  cli::cli_abort(c(
+    "{.code complete = TRUE} is not supported for this query.",
+    x = reason,
+    i = alternative
+  ), class = "uscogdata_complete_unsupported")
+}
+
+#' @noRd
+.require_representation <- function(con, manifest) {
+  needed <- c("representation.parquet", "code_set.parquet")
+  missing <- needed[!vapply(needed, function(f) .corpus_has_table(manifest, f),
+                            logical(1))]
+  if (length(missing) == 0L) return(invisible(TRUE))
+  cli::cli_abort(c(
+    "This corpus does not publish the representation contract.",
+    x = "Missing: {.file {missing}}.",
+    i = "{.code complete = TRUE} needs those tables to know whether an absent cell means Census published $0 or means the government did not report.",
+    i = "They ship with corpora published from 2026-07-29 onward; re-point {.envvar USCOGDATA_URL} at a current corpus, or omit {.code complete}."
+  ), class = "uscogdata_representation_unavailable")
+}
+
+#' The cells a government-year COULD carry: every code in force for that
+#' government's own type, mapped through `summary_categories`, restricted to
+#' the calling verb's flow prefixes and (when given) its category filter.
+#'
+#' Scoped by `govs_type` deliberately. Filling against the union of all types
+#' would invent cells that the government can never report -- a county row for
+#' "state IG transfer to school districts" -- and those inventions would then
+#' be indistinguishable from real census zeros.
+#'
+#' `NOT cs.is_aggregate` mirrors `spending_long` / `revenue_long`, which drop
+#' aggregate rows. Without it the grid would offer cells the verb structurally
+#' never returns, so every one of them would fill as a phantom $0.
+#' @noRd
+.completion_grid_sql <- function(subtype_col, govid, years, category,
+                                 flow_prefixes) {
+  category_pred <- if (is.null(category)) {
+    ""
+  } else {
+    sprintf("AND c.category IN (%s)", .sql_lit_chr(category))
+  }
+  sprintf(
+    "SELECT DISTINCT
+       cs.year,
+       x.canonical_govid,
+       x.gov_name,
+       c.%1$s AS subtype_value,
+       c.category,
+       r.absence_means
+     FROM code_set cs
+     JOIN canonical_fips_xwalk x ON x.govs_type = cs.type
+     JOIN summary_categories c   ON c.item_code = cs.item_code
+     JOIN representation r       ON r.year = cs.year
+     WHERE x.canonical_govid IN (%2$s)
+       AND cs.year IN (%3$s)
+       AND NOT cs.is_aggregate
+       AND LEFT(cs.item_code, 1) IN (%4$s)
+       AND c.category IS NOT NULL
+       AND c.%1$s IS NOT NULL
+       %5$s",
+    subtype_col, .sql_lit_chr(govid),
+    paste(as.integer(years), collapse = ","),
+    .sql_lit_chr(flow_prefixes), category_pred
+  )
+}
+
+#' Fill `result` out to the full grid, stamping `value_source` on every row.
+#'
+#' Returns the completed tibble with a `.completion` attribute carrying the
+#' provenance block. Reported rows are passed through untouched -- filling
+#' must never alter or drop what the corpus actually published.
+#' @noRd
+.complete_result <- function(result, con, subtype_col, govid, years, category,
+                             flow_prefixes) {
+  grid <- tibble::as_tibble(DBI::dbGetQuery(
+    con, .completion_grid_sql(subtype_col, govid, years, category, flow_prefixes)
+  ))
+
+  result$value_source <- rep("reported", nrow(result))
+  if (nrow(grid) == 0L) {
+    attr(result, ".completion") <- list(
+      applied = TRUE, rows_filled = 0L, absence_means = list()
+    )
+    return(result)
+  }
+
+  names(grid)[names(grid) == "subtype_value"] <- subtype_col
+  key <- function(d) {
+    paste(d$year, d$canonical_govid, d[[subtype_col]], d$category, sep = "\r")
+  }
+  missing <- grid[!key(grid) %in% key(result), , drop = FALSE]
+
+  if (nrow(missing) > 0L) {
+    filled <- tibble::tibble(
+      year            = as.integer(missing$year),
+      canonical_govid = as.character(missing$canonical_govid),
+      gov_name        = as.character(missing$gov_name),
+      category        = as.character(missing$category),
+      # census_zero is a value Census published; not_reported is unknown and
+      # must stay NA. Collapsing the two to 0 is the defect, not the fill.
+      amt_nominal     = ifelse(missing$absence_means == "census_zero",
+                               0, NA_real_),
+      codes_included  = NA_character_,
+      aggregate_fallback = NA,
+      value_source    = as.character(missing$absence_means)
+    )
+    filled[[subtype_col]] <- as.character(missing[[subtype_col]])
+    if ("notes" %in% names(result)) filled$notes <- NA_character_
+
+    result <- dplyr::bind_rows(result, filled)
+    result <- result[order(result$year, result$canonical_govid,
+                           result[[subtype_col]], result$category), ,
+                     drop = FALSE]
+  }
+
+  rules <- unique(grid[, c("year", "absence_means")])
+  attr(result, ".completion") <- list(
+    applied = TRUE,
+    rows_filled = nrow(missing),
+    absence_means = stats::setNames(
+      as.list(as.character(rules$absence_means)), as.character(rules$year)
+    )
+  )
+  result
+}
diff --git a/R/explain.R b/R/explain.R
index aedbda4..55d2c34 100644
--- a/R/explain.R
+++ b/R/explain.R
@@ -118,6 +118,24 @@ cog_explain <- function(result, format = c("print", "list")) {
     cli::cli_ul(sugg_lines)
   }
 
+  if (isTRUE(prov$completion$applied)) {
+    cli::cli_h2("Completion")
+    cli::cli_text(
+      "Filled {prov$completion$rows_filled} absent cell(s) from the corpus code set."
+    )
+    rules <- prov$completion$absence_means
+    if (length(rules) > 0L) {
+      cli::cli_ul(vapply(names(rules), function(y) {
+        sprintf("%s: an absent cell means %s", y,
+                if (identical(rules[[y]], "census_zero")) {
+                  "Census published $0 (filled as 0)"
+                } else {
+                  "the government did not report (filled as NA, not 0)"
+                })
+      }, character(1)))
+    }
+  }
+
   if (length(prov$series_break_refs) > 0L) {
     cli::cli_h2("Series breaks")
     cli::cli_ul(.series_break_story_lines(prov$series_break_refs))
diff --git a/R/provenance.R b/R/provenance.R
index b521423..7b46220 100644
--- a/R/provenance.R
+++ b/R/provenance.R
@@ -10,7 +10,8 @@
                               expenditure_concept_note = NA_character_,
                               expenditure_concept_direct_suppressed = FALSE,
                               harmonization = NULL, recipe = NULL,
-                              suggestions = list()) {
+                              suggestions = list(),
+                              completion = NULL) {
   manifest <- .uscogdata_env$manifest
 
   codes <- result[["codes_included"]]
@@ -126,6 +127,13 @@
     ),
     series_break_refs = break_refs,
     corpus_break_refs = corpus_refs,
+    # What `complete = TRUE` filled, and the rule it filled by. Always
+    # present so a consumer can read `completion$applied` without testing
+    # for the key -- an absent block and applied = FALSE would otherwise be
+    # indistinguishable from an older reader version.
+    completion = completion %||% list(
+      applied = FALSE, rows_filled = 0L, absence_means = list()
+    ),
     manifest = list(
       schema_version = as.integer(manifest$schema_version),
       pipeline_commit = manifest$pipeline_commit %||% NA_character_,
diff --git a/R/revenue.R b/R/revenue.R
index ed71d08..eb11dd0 100644
--- a/R/revenue.R
+++ b/R/revenue.R
@@ -11,11 +11,13 @@
 #' @return Tibble with columns `year`, `canonical_govid`, `gov_name`,
 #'   `revenue_subtype`, `category`, `amt_nominal`, optional `amt_real`,
 #'   optional `amt_per_capita_nominal`, optional `amt_per_capita_real`,
-#'   optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`.
+#'   optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`,
+#'   and `value_source` when `complete = TRUE`.
 #' @export
 cog_revenue <- function(govid, years, category = NULL,
                         per_capita = FALSE, adjust_to_year = NULL,
-                        basis = c("harmonized", "raw"), recipe = NULL) {
+                        basis = c("harmonized", "raw"), recipe = NULL,
+                        complete = FALSE) {
   .verb_spendrev(
     verb           = "cog_revenue",
     view_base      = "revenue_annotated",
@@ -28,6 +30,7 @@ cog_revenue <- function(govid, years, category = NULL,
     per_capita     = per_capita,
     adjust_to_year = adjust_to_year,
     basis          = basis,
-    recipe         = recipe
+    recipe         = recipe,
+    complete       = complete
   )
 }
diff --git a/R/spending.R b/R/spending.R
index 80a9064..7ab4b5f 100644
--- a/R/spending.R
+++ b/R/spending.R
@@ -70,16 +70,42 @@
 #'   `provenance$expenditure_concept_direct_suppressed` is `TRUE` -- the
 #'   figure in those rows is the intergovernmental leg alone, not Direct +
 #'   IG.
+#' @param complete If `TRUE`, fill the requested grid so that a cell the
+#'   corpus does not carry still appears, labelled with **why** it is
+#'   missing, and add a `value_source` column to every row:
+#'
+#'   * `"reported"` — the corpus carries this cell.
+#'   * `"census_zero"` — dense-source year (`<= FY2011`), cell absent:
+#'     Census published `$0`. `amt_nominal` is `0`.
+#'   * `"not_reported"` — sparse-source year (`>= FY2012`), cell absent: the
+#'     government did not report, and the value is unknown. `amt_nominal` is
+#'     `NA`, **not** `0` — writing a zero there would invent data.
+#'
+#'   The grid comes from the corpus's `code_set` table, scoped to each
+#'   government's own type, so a county is never filled with cells only a
+#'   state can report. Reported rows are passed through untouched.
+#'
+#'   Defaults to `FALSE` (the historical behaviour: absent cells simply do
+#'   not appear). Needs a corpus published from 2026-07-29 onward, which is
+#'   when `representation`/`code_set` began shipping; aborts with class
+#'   `uscogdata_representation_unavailable` otherwise. Not available with
+#'   `recipe` or with `expenditure_concept = "total"` (class
+#'   `uscogdata_complete_unsupported`) — neither draws its cells from
+#'   `code_set`.
 #' @return Tibble with columns `year`, `canonical_govid`, `gov_name`,
 #'   `spend_subtype`, `category`, `amt_nominal`, optional `amt_real`,
 #'   optional `amt_per_capita_nominal`, optional `amt_per_capita_real`,
-#'   optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`.
-#'   Carries a `provenance` attribute matching `inst/schemas/provenance-v1.json`.
+#'   optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`,
+#'   and `value_source` when `complete = TRUE`.
+#'   Carries a `provenance` attribute matching `inst/schemas/provenance-v1.json`,
+#'   whose `completion` block reports `applied`, `rows_filled`, and the
+#'   per-year `absence_means` rule that was applied.
 #' @export
 cog_spending <- function(govid, years, category = NULL,
                          per_capita = FALSE, adjust_to_year = NULL,
                          basis = c("harmonized", "raw"), recipe = NULL,
-                         expenditure_concept = c("direct", "total")) {
+                         expenditure_concept = c("direct", "total"),
+                         complete = FALSE) {
   .verb_spendrev(
     verb          = "cog_spending",
     view_base     = "spending_annotated",
@@ -93,7 +119,8 @@ cog_spending <- function(govid, years, category = NULL,
     adjust_to_year = adjust_to_year,
     basis         = basis,
     recipe        = recipe,
-    expenditure_concept = expenditure_concept
+    expenditure_concept = expenditure_concept,
+    complete      = complete
   )
 }
 
@@ -118,7 +145,8 @@ cog_spending <- function(govid, years, category = NULL,
                            govid, years, category,
                            per_capita, adjust_to_year,
                            basis = c("harmonized", "raw"), recipe = NULL,
-                           expenditure_concept = c("direct", "total")) {
+                           expenditure_concept = c("direct", "total"),
+                           complete = FALSE) {
   basis_explicit <- length(basis) == 1L
   basis <- match.arg(basis, c("harmonized", "raw"))
   # match.arg() itself throws a base `simpleError`, not an rlang-classed
@@ -165,12 +193,27 @@ cog_spending <- function(govid, years, category = NULL,
     )
   }
 
+  complete <- isTRUE(complete)
+  if (complete && !is.null(recipe)) {
+    .abort_complete_unsupported(
+      "A recipe defines its own component codes and never goes through `summary_categories`, so there is no grid to fill from.",
+      "Query the recipe without `complete`, or use a category query with `complete = TRUE`."
+    )
+  }
+  if (complete && identical(expenditure_concept, "total")) {
+    .abort_complete_unsupported(
+      "The intergovernmental leg deliberately keeps aggregate-flagged rows (see `inst/sql/24-ig_long.sql`), so its cells are not the ones `code_set` describes.",
+      "Use `expenditure_concept = \"direct\"` with `complete = TRUE`, or drop `complete`."
+    )
+  }
+
   years   <- as.integer(years)
   if (!is.null(adjust_to_year)) adjust_to_year <- as.integer(adjust_to_year)
 
   con <- .ensure_session()
   manifest <- .uscogdata_env$manifest
   scope <- .check_govids_in_scope(govid)
+  if (complete) .require_representation(con, manifest)
 
   resolved <- .resolve_basis(basis, basis_explicit, manifest)
 
@@ -201,6 +244,18 @@ cog_spending <- function(govid, years, category = NULL,
     result <- tibble::as_tibble(DBI::dbGetQuery(con, sql))
   }
 
+  # Fill BEFORE per_capita / inflation so the added cells get the same
+  # treatment as reported ones: a census_zero stays $0 per capita and in real
+  # dollars, and a not_reported stays NA through both rather than becoming a
+  # spurious 0.
+  completion <- list(applied = FALSE, rows_filled = 0L, absence_means = list())
+  if (complete) {
+    result <- .complete_result(result, con, subtype_col, govid, years,
+                               category, flow_prefixes)
+    completion <- attr(result, ".completion")
+    attr(result, ".completion") <- NULL
+  }
+
   if (per_capita) result <- .attach_per_capita(result, con, govid)
   if (!is.null(adjust_to_year)) {
     result <- .attach_real_dollars(result, adjust_to_year, per_capita)
@@ -309,7 +364,8 @@ cog_spending <- function(govid, years, category = NULL,
     expenditure_concept_direct_suppressed = direct_suppressed_flag,
     harmonization  = harmonization,
     recipe         = recipe_block,
-    suggestions    = suggestions
+    suggestions    = suggestions,
+    completion     = completion
   )
   prov$scope$govids_found   <- scope$found
   prov$scope$govids_missing <- scope$missing
diff --git a/R/views.R b/R/views.R
index c5febdd..172d6e9 100644
--- a/R/views.R
+++ b/R/views.R
@@ -32,6 +32,29 @@
   "45-ig_annotated_harmonized.sql"
 )
 
+# The representation contract (cog_pipeline#64): two parquet tables that say
+# what an ABSENT cell means in a given year. Gated on manifest PRESENCE, not
+# on schema_version, because the sparsification that introduced them did not
+# bump the version -- the pre-sparsification corpus this package shipped
+# against until 2026-07-30 was already schema v6 and carried neither table.
+# Keying off the version number would therefore register a view over a file
+# that does not exist and fail at CREATE VIEW time on exactly the corpora this
+# check exists to tolerate.
+.representation_view_files <- c(
+  "36-representation.sql" = "representation.parquet",
+  "37-code_set.sql"       = "code_set.parquet"
+)
+
+#' Does the mounted corpus publish `file` (e.g. "code_set.parquet")?
+#' Reads the manifest's metadata list rather than stat-ing the URL, so it
+#' works identically for a local fixture and a remote share.
+#' @noRd
+.corpus_has_table <- function(manifest, file) {
+  paths <- vapply(manifest$files$metadata %||% list(),
+                  function(f) as.character(f$path %||% ""), character(1))
+  file %in% basename(paths)
+}
+
 #' Register DuckDB views from inst/sql/ SQL files
 #' @noRd
 .register_views <- function(con, url, manifest) {
@@ -39,7 +62,10 @@
   files   <- sort(list.files(sql_dir, pattern = "\\.sql$", full.names = TRUE))
   schema_version <- suppressWarnings(as.integer(manifest$schema_version %||% 0L))
   for (f in files) {
-    if (basename(f) %in% .harmonization_view_files && schema_version < 5L) next
+    base <- basename(f)
+    if (base %in% .harmonization_view_files && schema_version < 5L) next
+    if (base %in% names(.representation_view_files) &&
+        !.corpus_has_table(manifest, .representation_view_files[[base]])) next
     sql <- paste(readLines(f, warn = FALSE), collapse = "\n")
     sql <- gsub("\\{url\\}", url, sql, fixed = FALSE)
     DBI::dbExecute(con, sql)
diff --git a/inst/schemas/provenance-v1.json b/inst/schemas/provenance-v1.json
index 814b29b..6307533 100644
--- a/inst/schemas/provenance-v1.json
+++ b/inst/schemas/provenance-v1.json
@@ -33,6 +33,15 @@
     "aggregate_fallback": { "type": ["object", "null"] },
     "transformations":{ "type": "object" },
     "series_break_refs": { "type": "array", "items": { "type": "string" } },
+    "completion": {
+      "type": "object",
+      "description": "What `complete = TRUE` filled. `applied` is FALSE on an ordinary query. `rows_filled` counts cells added to the requested grid, and `absence_means` maps each requested year to the meaning of an absent cell there ('census_zero' in a dense_source year, 'not_reported' in a sparse_source one). Filled rows carry `value_source` in the result: 'reported', 'census_zero' (amount 0 -- Census published $0), or 'not_reported' (amount NA -- unknown).",
+      "properties": {
+        "applied": { "type": "boolean" },
+        "rows_filled": { "type": "integer" },
+        "absence_means": { "type": "object" }
+      }
+    },
     "corpus_break_refs": {
       "type": "array",
       "items": { "type": "string" },
diff --git a/inst/sql/36-representation.sql b/inst/sql/36-representation.sql
new file mode 100644
index 0000000..ac878c3
--- /dev/null
+++ b/inst/sql/36-representation.sql
@@ -0,0 +1,3 @@
+CREATE OR REPLACE VIEW representation AS
+SELECT *
+FROM read_parquet('{url}data/representation.parquet');
diff --git a/inst/sql/37-code_set.sql b/inst/sql/37-code_set.sql
new file mode 100644
index 0000000..8905bc8
--- /dev/null
+++ b/inst/sql/37-code_set.sql
@@ -0,0 +1,3 @@
+CREATE OR REPLACE VIEW code_set AS
+SELECT *
+FROM read_parquet('{url}data/code_set.parquet');
diff --git a/man/cog_revenue.Rd b/man/cog_revenue.Rd
index 843d48e..b018fef 100644
--- a/man/cog_revenue.Rd
+++ b/man/cog_revenue.Rd
@@ -11,7 +11,8 @@ cog_revenue(
   per_capita = FALSE,
   adjust_to_year = NULL,
   basis = c("harmonized", "raw"),
-  recipe = NULL
+  recipe = NULL,
+  complete = FALSE
 )
 }
 \arguments{
@@ -55,12 +56,36 @@ argument is ignored and the result's provenance reports
 `basis = "recipe"` with an inert `harmonization` block (`applied =
 FALSE`, pointing at the `recipe` block instead) rather than a
 possibly-misleading `"harmonized"`/`"raw"` value.}
+
+\item{complete}{If `TRUE`, fill the requested grid so that a cell the
+  corpus does not carry still appears, labelled with **why** it is
+  missing, and add a `value_source` column to every row:
+
+  * `"reported"` — the corpus carries this cell.
+  * `"census_zero"` — dense-source year (`<= FY2011`), cell absent:
+    Census published `$0`. `amt_nominal` is `0`.
+  * `"not_reported"` — sparse-source year (`>= FY2012`), cell absent: the
+    government did not report, and the value is unknown. `amt_nominal` is
+    `NA`, **not** `0` — writing a zero there would invent data.
+
+  The grid comes from the corpus's `code_set` table, scoped to each
+  government's own type, so a county is never filled with cells only a
+  state can report. Reported rows are passed through untouched.
+
+  Defaults to `FALSE` (the historical behaviour: absent cells simply do
+  not appear). Needs a corpus published from 2026-07-29 onward, which is
+  when `representation`/`code_set` began shipping; aborts with class
+  `uscogdata_representation_unavailable` otherwise. Not available with
+  `recipe` or with `expenditure_concept = "total"` (class
+  `uscogdata_complete_unsupported`) — neither draws its cells from
+  `code_set`.}
 }
 \value{
 Tibble with columns `year`, `canonical_govid`, `gov_name`,
   `revenue_subtype`, `category`, `amt_nominal`, optional `amt_real`,
   optional `amt_per_capita_nominal`, optional `amt_per_capita_real`,
-  optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`.
+  optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`,
+  and `value_source` when `complete = TRUE`.
 }
 \description{
 Mirror of [cog_spending()] for revenue categories. One row per
diff --git a/man/cog_spending.Rd b/man/cog_spending.Rd
index 45f8d11..9638efa 100644
--- a/man/cog_spending.Rd
+++ b/man/cog_spending.Rd
@@ -12,7 +12,8 @@ cog_spending(
   adjust_to_year = NULL,
   basis = c("harmonized", "raw"),
   recipe = NULL,
-  expenditure_concept = c("direct", "total")
+  expenditure_concept = c("direct", "total"),
+  complete = FALSE
 )
 }
 \arguments{
@@ -58,40 +59,66 @@ FALSE`, pointing at the `recipe` block instead) rather than a
 possibly-misleading `"harmonized"`/`"raw"` value.}
 
 \item{expenditure_concept}{`"direct"` (default) returns only the
-government's own direct spending (item codes `E`/`F`/`G`), unchanged
-from prior releases. `"total"` additionally UNIONs in the
-intergovernmental leg -- payments to local governments (`M` codes) and
-to the state government (`L` codes, excluding the `L--` family-total
-rollup) -- so results gain rows with `spend_subtype ==
-"intergovernmental"`. Requires the active corpus's `summary_categories`
-to carry M/L rows (added by cog_pipeline PR #59); aborts with class
-`uscogdata_ig_categories_unsupported` on an older corpus rather than
-silently under-reporting. Mutually exclusive with `recipe` (a recipe
-already defines its own component codes). **Do not sum `"total"`
-results across levels of government** (e.g. state + county + city):
-a state's `M12` payment to a school district is the same dollar the
-district reports as its own direct `E12`, so summing both double-counts
-it. This matters in particular with [cog_geographic_rollup()], which
-sums across exactly that kind of multi-layer government set.
+  government's own direct spending (item codes `E`/`F`/`G`), unchanged
+  from prior releases. `"total"` additionally UNIONs in the
+  intergovernmental leg -- payments to local governments (`M` codes) and
+  to the state government (`L` codes, excluding the `L--` family-total
+  rollup) -- so results gain rows with `spend_subtype ==
+  "intergovernmental"`. Requires the active corpus's `summary_categories`
+  to carry M/L rows (added by cog_pipeline PR #59); aborts with class
+  `uscogdata_ig_categories_unsupported` on an older corpus rather than
+  silently under-reporting. Mutually exclusive with `recipe` (a recipe
+  already defines its own component codes). **Do not sum `"total"`
+  results across levels of government** (e.g. state + county + city):
+  a state's `M12` payment to a school district is the same dollar the
+  district reports as its own direct `E12`, so summing both double-counts
+  it. This matters in particular with [cog_geographic_rollup()], which
+  sums across exactly that kind of multi-layer government set.
 
-In the legacy wide era (<= FY2011), some functions are published ONLY
-as an aggregate-flagged family total (e.g. Corrections' `E04`/`E05`
-split), which the Direct leg excludes by construction but the IG leg
-deliberately keeps (see `inst/sql/24-ig_long.sql`). For a `"total"`
-query, any (year, category) where this leaves intergovernmental rows
-with NO Direct counterpart is flagged: the affected rows' `notes`
-name the harmonization recipe that recovers the missing Direct
-component (when one exists), and
-`provenance$expenditure_concept_direct_suppressed` is `TRUE` -- the
-figure in those rows is the intergovernmental leg alone, not Direct +
-IG.}
+  In the legacy wide era (<= FY2011), some functions are published ONLY
+  as an aggregate-flagged family total (e.g. Corrections' `E04`/`E05`
+  split), which the Direct leg excludes by construction but the IG leg
+  deliberately keeps (see `inst/sql/24-ig_long.sql`). For a `"total"`
+  query, any (year, category) where this leaves intergovernmental rows
+  with NO Direct counterpart is flagged: the affected rows' `notes`
+  name the harmonization recipe that recovers the missing Direct
+  component (when one exists), and
+  `provenance$expenditure_concept_direct_suppressed` is `TRUE` -- the
+  figure in those rows is the intergovernmental leg alone, not Direct +
+  IG.}
+
+\item{complete}{If `TRUE`, fill the requested grid so that a cell the
+  corpus does not carry still appears, labelled with **why** it is
+  missing, and add a `value_source` column to every row:
+
+  * `"reported"` — the corpus carries this cell.
+  * `"census_zero"` — dense-source year (`<= FY2011`), cell absent:
+    Census published `$0`. `amt_nominal` is `0`.
+  * `"not_reported"` — sparse-source year (`>= FY2012`), cell absent: the
+    government did not report, and the value is unknown. `amt_nominal` is
+    `NA`, **not** `0` — writing a zero there would invent data.
+
+  The grid comes from the corpus's `code_set` table, scoped to each
+  government's own type, so a county is never filled with cells only a
+  state can report. Reported rows are passed through untouched.
+
+  Defaults to `FALSE` (the historical behaviour: absent cells simply do
+  not appear). Needs a corpus published from 2026-07-29 onward, which is
+  when `representation`/`code_set` began shipping; aborts with class
+  `uscogdata_representation_unavailable` otherwise. Not available with
+  `recipe` or with `expenditure_concept = "total"` (class
+  `uscogdata_complete_unsupported`) — neither draws its cells from
+  `code_set`.}
 }
 \value{
 Tibble with columns `year`, `canonical_govid`, `gov_name`,
   `spend_subtype`, `category`, `amt_nominal`, optional `amt_real`,
   optional `amt_per_capita_nominal`, optional `amt_per_capita_real`,
-  optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`.
-  Carries a `provenance` attribute matching `inst/schemas/provenance-v1.json`.
+  optional `pop_source`, `codes_included`, `aggregate_fallback`, `notes`,
+  and `value_source` when `complete = TRUE`.
+  Carries a `provenance` attribute matching `inst/schemas/provenance-v1.json`,
+  whose `completion` block reports `applied`, `rows_filled`, and the
+  per-year `absence_means` rule that was applied.
 }
 \description{
 One row per `(year, canonical_govid, spend_subtype, category)`. Amounts are
diff --git a/tests/testthat/helper-fixture.R b/tests/testthat/helper-fixture.R
index 47f0726..3ea3744 100644
--- a/tests/testthat/helper-fixture.R
+++ b/tests/testthat/helper-fixture.R
@@ -85,6 +85,42 @@ with_doctored_schema_version <- function(version, code) {
   force(code)
 }
 
+# Copy the bundled fixture to a temp dir with representation.parquet and
+# code_set.parquet removed (and dropped from the manifest's metadata list),
+# then run `code` against it. Models a corpus published BEFORE sparsification:
+# schema_version is left alone deliberately, because it was never bumped for
+# that change -- the pre-sparsification fixture this package shipped until
+# 2026-07-30 was schema v6 and carried neither table. Presence in the manifest
+# is therefore the only honest signal, and this helper is what proves the
+# package keys off it rather than off the version number.
+with_corpus_missing_representation <- function(code) {
+  src <- fixture_corpus_path()
+  tmp <- withr::local_tempdir(.local_envir = parent.frame())
+  file.copy(list.files(src, full.names = TRUE), tmp, recursive = TRUE)
+
+  dropped <- c("representation.parquet", "code_set.parquet")
+  file.remove(file.path(tmp, "data", dropped))
+
+  manifest_path <- file.path(tmp, "manifest.json")
+  m <- jsonlite::fromJSON(manifest_path, simplifyVector = FALSE)
+  m$files$metadata <- Filter(
+    function(f) !basename(f$path) %in% dropped, m$files$metadata
+  )
+  writeLines(
+    jsonlite::toJSON(m, auto_unbox = TRUE, pretty = TRUE, null = "null"),
+    manifest_path
+  )
+
+  old_url <- Sys.getenv("USCOGDATA_URL", unset = NA)
+  uscogdata:::cog_close()
+  Sys.setenv(USCOGDATA_URL = paste0(tmp, "/"))
+  on.exit({
+    uscogdata:::cog_close()
+    if (is.na(old_url)) Sys.unsetenv("USCOGDATA_URL") else Sys.setenv(USCOGDATA_URL = old_url)
+  }, add = TRUE)
+  force(code)
+}
+
 # Copy the bundled fixture to a temp dir with summary_categories.parquet
 # rewritten to drop every M/L (intergovernmental) row, then run `code`
 # against it with a clean session (mirrors with_fixture_corpus()/
diff --git a/tests/testthat/test-complete.R b/tests/testthat/test-complete.R
new file mode 100644
index 0000000..4a2c771
--- /dev/null
+++ b/tests/testthat/test-complete.R
@@ -0,0 +1,188 @@
+# tests/testthat/test-complete.R
+#
+# uscogdata#18. The published corpus no longer stores the wide era's explicit
+# zeros (cog_pipeline#64, series break SB194), so absence means two different
+# things:
+#
+#   <= FY2011 (dense_source) : cell absent => Census published $0
+#   >= FY2012 (sparse_source): cell absent => not reported, unknown
+#
+# `complete = TRUE` fills the requested grid from `code_set` and stamps every
+# row's `value_source` so the two are distinguishable. Expected row sets here
+# are built from the corpus parquet directly, never from the verb under test --
+# verifying what a filter does through that same filter proves nothing.
+
+# The (subtype, category) cells that SHOULD exist for one government-year:
+# every code in force for that government's type, mapped through
+# summary_categories, matching the verb's flow prefixes and excluding
+# aggregate-flagged codes (which spending_long/revenue_long drop).
+raw_expected_cells <- function(govid, year, prefixes, subtype_col) {
+  fx <- sub("/$", "", Sys.getenv("USCOGDATA_URL"))
+  q <- function(f) sprintf("read_parquet('%s/data/%s')", fx, f)
+  wt_raw_query(sprintf(
+    "SELECT DISTINCT c.%s AS subtype, c.category
+     FROM %s cs
+     JOIN %s x ON x.govs_type = cs.type
+     JOIN %s c ON c.item_code = cs.item_code
+     WHERE x.canonical_govid = '%s'
+       AND cs.year = %d
+       AND NOT cs.is_aggregate
+       AND LEFT(cs.item_code, 1) IN (%s)
+       AND c.category IS NOT NULL
+       AND c.%s IS NOT NULL",
+    subtype_col, q("code_set.parquet"), q("canonical_fips_xwalk.parquet"),
+    q("summary_categories.parquet"), govid, year,
+    paste0("'", prefixes, "'", collapse = ","), subtype_col
+  ))
+}
+
+test_that("complete = FALSE is the default and changes nothing", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    plain <- cog_spending("121011212191", 2011L)
+    explicit <- cog_spending("121011212191", 2011L, complete = FALSE)
+    expect_equal(nrow(plain), nrow(explicit))
+    expect_false("value_source" %in% names(plain))
+  })
+})
+
+test_that("complete = TRUE round-trips a dense-source year to the pre-sparsification cells", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    # FY2011 is dense_source: before sparsification this government carried a
+    # row for every code in force, most of them $0. complete = TRUE must
+    # reproduce that cell set exactly.
+    r <- cog_spending("121011212191", 2011L, complete = TRUE)
+    expected <- raw_expected_cells("121011212191", 2011L,
+                                   c("E", "F", "G"), "spend_subtype")
+
+    key <- function(sub, cat) paste(sub, cat, sep = "|")
+    expect_setequal(key(r$spend_subtype, r$category),
+                    key(expected$subtype, expected$category))
+    expect_gt(nrow(expected), 0L)
+
+    # Every filled cell in a dense-source year is a Census-published $0 --
+    # never "unknown", which is what the modern era's absences mean.
+    expect_setequal(unique(r$value_source), c("reported", "census_zero"))
+    expect_true(all(r$amt_nominal[r$value_source == "census_zero"] == 0))
+    expect_true(all(r$amt_nominal[r$value_source == "reported"] != 0))
+  })
+})
+
+test_that("complete = TRUE preserves the reported rows and their amounts exactly", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    plain <- cog_spending("121011212191", 2011L)
+    full  <- cog_spending("121011212191", 2011L, complete = TRUE)
+
+    # Filling adds rows; it must never alter or drop one.
+    expect_gt(nrow(full), nrow(plain))
+    reported <- full[full$value_source == "reported", ]
+    expect_equal(nrow(reported), nrow(plain))
+    expect_equal(sum(reported$amt_nominal), sum(plain$amt_nominal))
+    # ... and the total is unchanged, because every added cell is $0.
+    expect_equal(sum(full$amt_nominal, na.rm = TRUE), sum(plain$amt_nominal))
+  })
+})
+
+test_that("a sparse-source year's absences are unknown, not zero", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    # FY2019 is sparse_source: an absent cell means the government did not
+    # report, which is NOT a zero. Filling those with 0 would invent data --
+    # the exact error the representation contract exists to prevent.
+    r <- cog_spending("121011212191", 2019L, complete = TRUE)
+    filled <- r[r$value_source != "reported", ]
+    expect_gt(nrow(filled), 0L)
+    expect_true(all(filled$value_source == "not_reported"))
+    expect_true(all(is.na(filled$amt_nominal)))
+    expect_false(any(r$value_source == "census_zero"))
+  })
+})
+
+test_that("the fill is scoped to each government's own type", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    # Filling against the union of all types would invent cells for codes a
+    # county can never report. Every filled category must be one that
+    # code_set puts in force for type 1 (county) specifically.
+    r <- cog_spending("121011212191", 2011L, complete = TRUE)
+    county_cells <- raw_expected_cells("121011212191", 2011L,
+                                       c("E", "F", "G"), "spend_subtype")
+    expect_true(all(r$category %in% county_cells$category))
+  })
+})
+
+test_that("complete = TRUE respects the category filter", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    r <- cog_spending("121011212191", 2011L, category = "Police",
+                      complete = TRUE)
+    expect_true(all(r$category == "Police"))
+    expect_true("value_source" %in% names(r))
+  })
+})
+
+test_that("cog_revenue() completes on its own flow", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    r <- cog_revenue("121011212191", 2011L, complete = TRUE)
+    expected <- raw_expected_cells("121011212191", 2011L,
+                                   c("T", "A", "U", "B", "C", "D"),
+                                   "revenue_subtype")
+    key <- function(sub, cat) paste(sub, cat, sep = "|")
+    expect_setequal(key(r$revenue_subtype, r$category),
+                    key(expected$subtype, expected$category))
+    expect_setequal(unique(r$value_source), c("reported", "census_zero"))
+  })
+})
+
+test_that("provenance records the completion and its absence rule", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    prov <- attr(cog_spending("121011212191", 2011L, complete = TRUE),
+                 "provenance")
+    expect_true(prov$completion$applied)
+    expect_equal(prov$completion$absence_means$`2011`, "census_zero")
+    expect_gt(prov$completion$rows_filled, 0L)
+
+    off <- attr(cog_spending("121011212191", 2011L), "provenance")
+    expect_false(off$completion$applied)
+    expect_equal(off$completion$rows_filled, 0L)
+  })
+})
+
+test_that("complete = TRUE is refused where the fill would be guesswork", {
+  skip_if_no_corpus()
+  with_fixture_corpus({
+    # A recipe defines its own component codes and does not go through
+    # summary_categories at all, so there is no grid to fill from.
+    expect_error(
+      cog_spending("121011212191", 2011L, recipe = "corrections_combined",
+                   complete = TRUE),
+      class = "uscogdata_complete_unsupported"
+    )
+    # The intergovernmental leg keeps aggregate rows by design
+    # (inst/sql/24-ig_long.sql), so its grid is not code_set's grid.
+    expect_error(
+      cog_spending("121011212191", 2011L, expenditure_concept = "total",
+                   complete = TRUE),
+      class = "uscogdata_complete_unsupported"
+    )
+  })
+})
+
+test_that("complete = TRUE aborts on a corpus with no representation contract", {
+  skip_if_no_corpus()
+  # A corpus published before sparsification carries neither table, so there
+  # is nothing to fill from and no rule saying what an absence means. That
+  # must abort rather than guess.
+  with_corpus_missing_representation({
+    expect_error(
+      cog_spending("121011212191", 2011L, complete = TRUE),
+      class = "uscogdata_representation_unavailable"
+    )
+    # ... while an ordinary query on the same corpus still works.
+    expect_gt(nrow(cog_spending("121011212191", 2011L)), 0L)
+  })
+})