author-coa-mapping

Skill: author-coa-mapping

Purpose: Build and validate the COA→statement-line mapping for a new entity. This is the genuinely reusable-per-company asset — the pivot engine is a commodity, but a correct mapping is bespoke and judgment-laden, and it is exactly where a misstatement hides. Treat authoring + validating the mapping as the deliverable, not an assumed input.

When to use

• Onboarding a new entity/company to the close autopilot.
• A chart of accounts changed (new accounts, reorg) and the mapping must be refreshed.

The mapping contract

A CSV, one row per GL account:

account,description,statement,section,line,normal_balance

• statement ∈ IS | BS
• section (IS) ∈ Revenue COGS OpEx OtherIncomeExpense Tax
• section (BS) ∈ CurrentAssets NonCurrentAssets CurrentLiabilities NonCurrentLiabilities Equity
• line — the statement line label the account rolls into
• normal_balance ∈ debit | credit (validation + documentation; presentation sign is derived from the section, which is what makes contra-accounts — e.g. accumulated depreciation — correct)

Authoring discipline

1. Every TB account must map to exactly one line. No account left behind — the engine blocks (--strict) on any unmapped account.
2. Classify by economic substance, not by account number. Interest expense is OtherIncomeExpense, not OpEx or COGS; a mis-map here silently distorts gross profit and operating income while net income still ties (see the negative fixture).
3. Contra-accounts stay in their asset/revenue section with their natural normal_balance; the engine signs them correctly from the section.
4. State the basis (accrual vs cash; GAAP vs management view) — house rule §3 #12.

Validate before you run

python3 scripts/statement_engine.py \
  --entity examples/meridian-robotics.json \
  --coa    <your-mapping>.csv \
  --tb     <your-trial-balance>.csv \
  --lint-map

--lint-map reports unmapped accounts, invalid statement/section values, bad normal_balance, and duplicates. A clean lint is the pre-build gate for the whole close cycle. Start from ../produce-gaap-statements/examples/coa-mapping.csv as a worked template.

Reuse note

The mapping is the per-entity unit of reuse. Keep one mapping CSV per entity beside its entity profile; the same engines then run unchanged for every company.