P3: depreciation straight-line by days through the final month, schedules by day (defects 22, 9, D-37)

The final month takes what the months before leave, spread over its days;
a disposed asset stops on its disposal day. A skipped month is caught up
in the month the run is made; a reversed run un-posts its month. New
schedules spread by day; equal-months schedules must start on the 1st.
Amounts round to the currency's own minor unit. Kani and Lean proofs; an
exhaustive search over runs, reversals and disposals.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

bookspec/examples/depreciation-disposal-before-a-later-run.toml

@@ -0,0 +1,146 @@
+id = "depreciation-disposal-before-a-later-run"
+title = "A disposal dated before a later month's run is refused until that run is reversed"
+rule = "A disposal is refused while a run of a month after the disposal's stands: crediting it back at the disposal day would leave the disposal month's accumulated depreciation a debit and its expense short at the month's end. Once that run is reversed, the disposal takes the depreciation of the days held."
+status = "CONVENTION"
+sources = ["ASC 360-10-35-4"]
+tags = ["depreciation", "disposal", "refusal", "later-run", "p3-defect-22"]
+
+[setup]
+currency = "USD"
+fiscal_year_start = "01-01"
+basis = "accrual"
+rounding = "half-away-from-zero"
+
+[[setup.accounts]]
+code = "1000"
+name = "Bank"
+type = "asset"
+
+[[setup.accounts]]
+code = "1500"
+name = "Equipment"
+type = "asset"
+
+[[setup.accounts]]
+code = "1510"
+name = "Accumulated Depreciation"
+type = "asset"
+
+[[setup.accounts]]
+code = "3000"
+name = "Capital"
+type = "equity"
+
+[[setup.accounts]]
+code = "6200"
+name = "Depreciation Expense"
+type = "expense"
+
+[[setup.accounts]]
+code = "7100"
+name = "Gain or Loss on Disposal"
+type = "revenue"
+
+# Asset X: 12,000.00, no salvage, 12 months from 2026-01-01 (1,000.00 a
+# month; December the final month).
+[[setup.assets]]
+id = "X"
+description = "Asset X"
+cost = "12000.00"
+salvage = "0.00"
+life_months = 12
+in_service = "2026-01-01"
+method = "straight_line"
+cost_account = "1500"
+accumulated_account = "1510"
+expense_account = "6200"
+
+[[events]]
+date = "2026-01-01"
+description = "Capital"
+lines = [
+  { account = "1000", side = "debit", amount = "12000.00" },
+  { account = "3000", side = "credit", amount = "12000.00" },
+]
+
+[[events]]
+date = "2026-01-01"
+description = "Bought asset X"
+lines = [
+  { account = "1500", side = "debit", amount = "12000.00" },
+  { account = "1000", side = "credit", amount = "12000.00" },
+]
+
+[[events]]
+run_depreciation = { asset = "X", period = "2026-01" }
+
+[[events]]
+run_depreciation = { asset = "X", period = "2026-02" }
+
+[[events]]
+run_depreciation = { asset = "X", period = "2026-03" }
+
+[[events]]
+run_depreciation = { asset = "X", period = "2026-04" }
+
+[[events]]
+run_depreciation = { asset = "X", period = "2026-05" }
+
+[[events]]
+run_depreciation = { asset = "X", period = "2026-06" }
+
+[[events]]
+run_depreciation = { asset = "X", period = "2026-07" }
+
+# Disposed of 2026-06-15 for 7,000.00, after July's run: refused, naming
+# July's run.
+[[events]]
+date = "2026-06-15"
+dispose_asset = { asset = "X", proceeds = "7000.00", proceeds_account = "1000", gain_loss_account = "7100" }
+refused = "depreciation_past_disposal"
+
+# July's run reversed, dated in July.
+[[events]]
+date = "2026-07-31"
+description = "Reverse event 9"
+reverses = 9
+
+[[events]]
+date = "2026-06-15"
+dispose_asset = { asset = "X", proceeds = "7000.00", proceeds_account = "1000", gain_loss_account = "7100" }
+
+# Hand check (worked without the code): January through June carry
+# 6,000.00 once July's run is reversed. Held through Jun 15: 5,000.00 +
+# 1,000.00 x 15/30 = 5,500.00, so June's run posted 500.00 past the
+# disposal day. Book value 6,500.00; gain 7,000.00 - 6,500.00 = 500.00.
+# Had the disposal taken July's run back at Jun 15 (1,500.00 credited),
+# June would end with accumulated depreciation a 1,000.00 debit and
+# 4,500.00 of expense.
+[[expect]]
+query = "disposal"
+asset = "X"
+
+[expect.values]
+final_depreciation = "0.00"
+catch_up_depreciation = "0.00"
+excess_depreciation = "500.00"
+accumulated = "6000.00"
+book_value = "6500.00"
+gain_loss = "500.00"
+
+[[expect]]
+query = "balances"
+as_of = "2026-06-30"
+
+[expect.values]
+"1510" = "0.00"
+"6200" = "5500.00"
+"7100" = "500.00"
+
+[[expect]]
+query = "balances"
+as_of = "2026-07-31"
+
+[expect.values]
+"1510" = "0.00"
+"6200" = "5500.00"