diff --git a/R/balance_caveats.R b/R/balance_caveats.R
index 711f66f..dc25401 100644
--- a/R/balance_caveats.R
+++ b/R/balance_caveats.R
@@ -17,16 +17,7 @@
 #' truncated relative to the requested span.
 #' @noRd
 .balance_caveats <- function(con, codes_observed, years) {
-  windows <- DBI::dbGetQuery(con,
-    "SELECT c.balance_subtype AS subtype,
-            MIN(l.year) AS year_min,
-            MAX(l.year) AS year_max
-     FROM balance_long l
-     JOIN summary_categories c USING (item_code)
-     WHERE c.balance_subtype IS NOT NULL
-     GROUP BY 1
-     ORDER BY 1"
-  )
+  cw <- .balance_coverage_windows(con)
 
   observed_subtypes <- if (length(codes_observed) == 0L) {
     character(0)
@@ -38,12 +29,6 @@
     ))$balance_subtype
   }
 
-  cw <- stats::setNames(
-    lapply(seq_len(nrow(windows)),
-           function(i) as.integer(c(windows$year_min[i], windows$year_max[i]))),
-    windows$subtype
-  )
-
   # A family is "truncated" when the caller asked for years outside the span
   # that family actually covers -- the FY2016 employee-retirement termination
   # and the FY2021 end of the W family are both this shape.
@@ -68,6 +53,44 @@
   )
 }
 
+#' Per-subtype [min year, max year] extents for EVERY balance subtype in the
+#' mounted corpus, memoised for the session.
+#'
+#' The query carries no govid and no year predicate -- its answer is a property
+#' of the mounted corpus alone and cannot change between calls -- but it scans
+#' the whole of `balance_long`, which measured 35% of `cog_balances()` runtime
+#' on the bundled fixture and would be a per-request throughput ceiling once
+#' cog-api#26 serves this verb over HTTP. Memoised in `.uscogdata_env` and
+#' invalidated by `cog_close()`, the same pattern as `.uscogdata_env$manifest`.
+#'
+#' Scope is deliberately corpus-wide rather than query-scoped: a caller asking
+#' "is there a family I missed?" needs every window. The observed-scoped field
+#' is `truncated`. Documented as such in inst/schemas/provenance-v1.json.
+#' @noRd
+.balance_coverage_windows <- function(con) {
+  cached <- .uscogdata_env$balance_coverage_windows
+  if (!is.null(cached)) return(cached)
+
+  windows <- DBI::dbGetQuery(con,
+    "SELECT c.balance_subtype AS subtype,
+            MIN(l.year) AS year_min,
+            MAX(l.year) AS year_max
+     FROM balance_long l
+     JOIN summary_categories c USING (item_code)
+     WHERE c.balance_subtype IS NOT NULL
+     GROUP BY 1
+     ORDER BY 1"
+  )
+
+  cw <- stats::setNames(
+    lapply(seq_len(nrow(windows)),
+           function(i) as.integer(c(windows$year_min[i], windows$year_max[i]))),
+    windows$subtype
+  )
+  .uscogdata_env$balance_coverage_windows <- cw
+  cw
+}
+
 #' TRUE the first time `key` is seen this session, FALSE thereafter.
 #' Reset by cog_close().
 #' @noRd
diff --git a/R/balances.R b/R/balances.R
index 5f755f3..4a9567d 100644
--- a/R/balances.R
+++ b/R/balances.R
@@ -44,14 +44,17 @@
 #' @return Tibble with columns `year`, `canonical_govid`, `gov_name`,
 #'   `balance_subtype`, `category`, `amt_nominal`, `codes_included`,
 #'   `aggregate_fallback`, plus optional `amt_per_capita_nominal` and
-#'   `pop_source` (when `per_capita = TRUE`), and optional `amt_real` and
-#'   `amt_per_capita_real` (when `adjust_to_year` is set). Amounts are full
-#'   US dollars.
+#'   `pop_source` (when `per_capita = TRUE`), optional `amt_real` (when
+#'   `adjust_to_year` is set), and optional `amt_per_capita_real` (only when
+#'   **both** `per_capita = TRUE` and `adjust_to_year` are set -- there is no
+#'   nominal per-capita column to deflate otherwise). Amounts are full US
+#'   dollars.
 #'
 #'   Carries a `provenance` attribute matching
 #'   `inst/schemas/provenance-v1.json`, whose `balance_caveats` block reports
-#'   `not_gaap`, `not_gaap_note`, `coverage_window` (measured per-subtype year
-#'   extents) and `truncated` (subtypes whose coverage falls short of the
+#'   `not_gaap`, `not_gaap_note`, `coverage_window` (measured year extents for
+#'   every balance subtype in the mounted corpus, not only the observed ones)
+#'   and `truncated` (the observed subtypes whose coverage falls short of the
 #'   requested years). `expenditure_concept`/`revenue_concept` are `NA` --
 #'   holdings are a stock, not a flow, so neither concept vocabulary applies.
 #' @export
@@ -60,8 +63,19 @@ cog_balances <- function(govid, years, category = NULL,
                          basis = c("harmonized", "raw"), recipe = NULL) {
   call <- match.call()
   basis <- match.arg(basis, c("harmonized", "raw"))
-  .validate_balance_inputs(per_capita, adjust_to_year)
+  # Coerce FIRST, validate second: .validate_verb_inputs() asserts
+  # is.character(govid), and a data-frame govid (cog_gov_search() output) has
+  # not been unwrapped yet at this point.
   govid <- .coerce_govid_input(govid)
+  # The money verbs' validator, reused rather than re-implemented (R/spending.R).
+  # It covers the exact superset cog_balances() needs -- including the
+  # recipe/category mutual-exclusivity guard -- so a second local copy would
+  # only be a place for the two to drift apart. This is the same kind of
+  # helper reuse as .build_verb_sql()/.attach_per_capita() below; it does NOT
+  # route the verb through .verb_spendrev(), which stays deliberately unused
+  # here because its flow vocabulary is meaningless for a stock.
+  .validate_verb_inputs(govid, years, category, per_capita, adjust_to_year,
+                        recipe)
   years <- as.integer(years)
   if (!is.null(adjust_to_year)) adjust_to_year <- as.integer(adjust_to_year)
 
@@ -129,24 +143,6 @@ cog_balances <- function(govid, years, category = NULL,
   result
 }
 
-#' Cheap type validation for the two arguments cog_balances() shares with the
-#' money verbs. Mirrors the per_capita/adjust_to_year checks in
-#' .validate_verb_inputs() (R/spending.R) -- category/recipe validation is
-#' deliberately out of scope here (uscogdata#25 Task 3 review note).
-#' @noRd
-.validate_balance_inputs <- function(per_capita, adjust_to_year) {
-  if (!is.logical(per_capita) || length(per_capita) != 1L) {
-    cli::cli_abort("`per_capita` must be a length-1 logical.")
-  }
-  if (!is.null(adjust_to_year)) {
-    if (!(is.integer(adjust_to_year) || is.numeric(adjust_to_year)) ||
-        length(adjust_to_year) != 1L) {
-      cli::cli_abort("`adjust_to_year` must be NULL or a length-1 integer.")
-    }
-  }
-  invisible(TRUE)
-}
-
 #' Abort unless the mounted corpus classifies balance codes.
 #'
 #' `balance_subtype` arrived with cog_pipeline #76/#77 without a
diff --git a/R/explain.R b/R/explain.R
index 5309e97..37380c4 100644
--- a/R/explain.R
+++ b/R/explain.R
@@ -68,6 +68,11 @@ cog_explain <- function(result, format = c("print", "list")) {
     if (!is.null(prov$revenue_concept)) {
       cli::cli_text("Concept: {prov$revenue_concept} revenue")
     }
+  } else if (identical(prov$verb, "cog_balances")) {
+    # Both concept fields are deliberately NA here (a stock has no flow
+    # concept). Printing the raw NA reads as a missing value rather than an
+    # intentional one, so say what it means instead.
+    cli::cli_text("Concept: not applicable (holdings are a stock, not a flow)")
   } else if (!is.null(prov$expenditure_concept)) {
     concept_note <- if (!is.null(prov$expenditure_concept_note) &&
                          !is.na(prov$expenditure_concept_note)) {
@@ -174,6 +179,31 @@ cog_explain <- function(result, format = c("print", "list")) {
     cli::cli_ul(.series_break_story_lines(prov$corpus_break_refs))
   }
 
+  # Balance results only (NULL on money-verb provenance, so they are
+  # unaffected). This is the ONLY on-demand surface for the GAAP disclosure:
+  # .emit_balance_caveats() fires at most once per session, and is routinely
+  # consumed by a suppressMessages() call or by a knitted chunk nobody reads,
+  # so a caller who deliberately audits a result with cog_explain() must still
+  # be told.
+  bc <- prov$balance_caveats
+  if (!is.null(bc)) {
+    cli::cli_h2("Holdings caveats")
+    if (!is.null(bc$not_gaap_note)) cli::cli_alert_warning(bc$not_gaap_note)
+    if (length(bc$truncated) > 0L) {
+      cli::cli_text(
+        "Requested years extend beyond what these families actually cover:"
+      )
+      cli::cli_ul(vapply(bc$truncated, function(s) {
+        w <- bc$coverage_window[[s]]
+        if (length(w) == 2L) {
+          sprintf("%s: covered %s-%s in this corpus", s, w[1], w[2])
+        } else {
+          s
+        }
+      }, character(1)))
+    }
+  }
+
   cli::cli_h2("Transformations")
   uc <- prov$transformations$units_conversion
   if (isTRUE(uc$applied)) {
diff --git a/R/session.R b/R/session.R
index 8f55887..ef1c28c 100644
--- a/R/session.R
+++ b/R/session.R
@@ -96,4 +96,6 @@ cog_close <- function() {
   .uscogdata_env$con      <- NULL
   .uscogdata_env$manifest <- NULL
   .uscogdata_env$balance_caveats_shown <- NULL
+  # Memoised corpus-constant; a different corpus may be mounted next.
+  .uscogdata_env$balance_coverage_windows <- NULL
 }
diff --git a/man/cog_balances.Rd b/man/cog_balances.Rd
index 9b96b97..f594eba 100644
--- a/man/cog_balances.Rd
+++ b/man/cog_balances.Rd
@@ -49,14 +49,17 @@ wide era to the modern one.}
 Tibble with columns `year`, `canonical_govid`, `gov_name`,
   `balance_subtype`, `category`, `amt_nominal`, `codes_included`,
   `aggregate_fallback`, plus optional `amt_per_capita_nominal` and
-  `pop_source` (when `per_capita = TRUE`), and optional `amt_real` and
-  `amt_per_capita_real` (when `adjust_to_year` is set). Amounts are full
-  US dollars.
+  `pop_source` (when `per_capita = TRUE`), optional `amt_real` (when
+  `adjust_to_year` is set), and optional `amt_per_capita_real` (only when
+  **both** `per_capita = TRUE` and `adjust_to_year` are set -- there is no
+  nominal per-capita column to deflate otherwise). Amounts are full US
+  dollars.
 
   Carries a `provenance` attribute matching
   `inst/schemas/provenance-v1.json`, whose `balance_caveats` block reports
-  `not_gaap`, `not_gaap_note`, `coverage_window` (measured per-subtype year
-  extents) and `truncated` (subtypes whose coverage falls short of the
+  `not_gaap`, `not_gaap_note`, `coverage_window` (measured year extents for
+  every balance subtype in the mounted corpus, not only the observed ones)
+  and `truncated` (the observed subtypes whose coverage falls short of the
   requested years). `expenditure_concept`/`revenue_concept` are `NA` --
   holdings are a stock, not a flow, so neither concept vocabulary applies.
 }