# Specification sources

wanderbooks' rules come from documents, not from anyone's memory. This
directory holds the authorities the engine's specs cite (`docs/spec/rules.md`
is the rule catalog), and every spec block in the code carries a `SOURCE:`
line pointing into it.

## The authority stack

There is no single "bible" of US bookkeeping. Authority is layered, and the
layers differ in what they cover and in whether we may copy them:

| Layer | What it governs | Copyright | Here |
|---|---|---|---|
| **Pacioli (1494), Geijsbeek translation (1914)** | The mechanics of double entry: debits equal credits, the trial balance, one money, writing only forward, correcting by opposite entry, closing into capital. No modern standard restates these; they predate every regulator. | Public domain | Vendored verbatim: `sources/pacioli-1494.md` |
| **IRS: Internal Revenue Code, Treasury Regulations, publications, form instructions** | Records and supporting documents, retention, accounting periods and methods, information returns (1099), capitalization (de minimis, 12-month rule), partners' capital, payroll taxes, rounding on returns, return line items for tax categories (`sources/irs-tax-lines.md`) | Public domain (17 U.S.C. §105; IRS.gov's content policy) | Vendored verbatim: `sources/irs-*.md`, `sources/us-public-domain-status.md` |
| **File formats: Intuit (QuickBooks Online bank CSV, QuickBooks Desktop IIF), ECMA-376 Office Open XML, Microsoft Excel limits** | What `ledger-import` reads and writes: bank/card CSV layouts and signs, IIF journal entries, how XLSX stores numbers and Excel's 15-digit precision | © Intuit Inc.; © Ecma International; © Microsoft | Cited with short quotes, URLs, and hashes: `sources/intuit-bank-csv.md`, `sources/intuit-iif.md`, `sources/xlsx-numbers.md` |
| **FASB Accounting Standards Codification (ASC)** | Authoritative US GAAP: cash flows (ASC 230), revenue and principal vs agent (ASC 606), foreign currency (ASC 830), credit losses and aging (ASC 326), property and depreciation (ASC 360) | © Financial Accounting Foundation | Cited by paragraph with short quotes only (in `rules.md`) |
| **FASB Concepts Statement No. 8, Chapter 4 (2021)** | Definitions of the five elements (it replaced Concepts Statement 6) | © Financial Accounting Foundation; non-authoritative | Cited with short quotes only |
| **Textbooks (OpenStax *Principles of Accounting, Vol. 1*)** | Conventions no standard states: normal balances, closing-entry mechanics, straight-line depreciation arithmetic | CC BY-NC-SA 4.0 (incompatible with this repo's license) | Cited with short quotes and attribution only |
| **Convention or decision** | Where no authority speaks: aging bucket edges, cent rounding among members, closed-period locks | — | Stated as CONVENTION or DECISION, with who decided and when |

## How to read a SOURCE line

```text
SOURCE: Pacioli ch. 36 (sources/pacioli-1494.md); IRS Pub. 583 (sources/irs-records.md)
SOURCE: ASC 830-20-30-1 (cited, rules.md B-3)
SOURCE: DECISION (Stephen, 2026-10-13)
SOURCE: CONVENTION (QuickBooks aging); nearest authority ASC 326-20-55-38 (illustrative)
```

A rule whose only source is CONVENTION or DECISION is a candidate for a
human to confirm or overturn; nothing else is.

## Rules added later never lock out older books

When a rule is tightened (a check added to a command), books written
before it must still open. Journal replay and the SQLite cross-check read
history through the engine's `replay_*` commands, which skip checks added
later; new commands go through the checked ones. Pinned by
`books_written_under_older_rules_still_open` (ledger-store).

## Vendoring rules

- Public-domain texts are copied **verbatim** (whitespace normalized), each
  with its URL, retrieval date, and the SHA-256 of the retrieved file, so
  anyone can check the excerpt against the original.
- Copyrighted sources are cited by paragraph, quoted briefly, never copied.
- When an authority changes (the IRS revises a publication; a statute is
  amended), add the new text beside the old with its effective date. Rules
  that depend on dates (1099 thresholds) must say which text applies when.
- Rules that change with the law are registered in
  `crates/ledger-core/src/rules.rs` with the years they are known for and
  a review date. Past what it knows, the engine refuses rather than
  guesses; from the review date, the MCP digest and the viewer flag the
  rule. Whoever updates one (human or agent) vendors the new official
  text here, extends the rule, and sends the change upstream: a pull
  request at https://github.com/swaits/wanderbooks (best), or an issue.

## Open: sources we could not verify

Read on 2026-10-13 through Deloitte's free DART roadmaps, which reproduce
ASC text: ASC 230-10-45-16 and -28, 326-20-55-37/38, 606-10-25-23, 45-2,
55-37/38, 830-20-30-1. Not yet verified (the ASC's free basic view needs a
login): ASC 360-10-35-4 (depreciation), 340-10 (prepaids), 230-10-45-10,
606-10-55-37B, 210 (balance sheet). Until someone with a FASB basic-view
account reads them, the rules that would cite them cite the textbook and
say so.