double-entry-accounting

# Double-Entry Accounting Agent applies foundational double-entry rules, ledger structure, and posting controls for accounting-domain work. ## When to Use | Prompt or Code Shape | Use | |---|---| | Ledger entries need balanced debit and credit lines | Agent uses this skill | | Domain models need chart-of-accounts, journal line, or general-ledger structure | Agent uses this skill | | Trial balance or posting validation rules are in scope | Agent uses this skill | | .NET services need deterministic debit-credit posting behavior | Agent uses this skill | ## When Not to Use | Prompt or Code Shape | Route | |---|---| | Work item covers approval states or posting workflow only | Agent uses `journal-entry-patterns` | | Work item covers reconciliation investigation only | Agent uses `reconciliation-patterns` | | Work item covers period close orchestration only | Agent uses `closing-cycle-patterns` | | Work item covers audit evidence or segregation controls only | Agent uses `audit-trail-compliance` | ## Required Inputs | Input | Required | Notes | |---|---|---| | Accounting equation policy | Yes | Agent confirms assets equal liabilities plus equity after posting. | | Account catalog | Yes | Agent maps account code, account type, and normal balance. | | Posting grain | Yes | Agent records header, line, currency, and effective date grain. | | Precision rule | Yes | Agent records decimal precision and rounding boundary. | | Posting source | No | Agent records subledger, import, or manual entry source when present. | ## Workflow | Step | Agent Action | Test | Pass | |---|---|---|---| | 1 | Agent maps every account to one account type and one normal balance. | Read account master data. | Every active account has one type and one normal balance. | | 2 | Agent validates each journal entry for equal debit and credit totals. | Sum debits and credits by entry. | Every accepted entry balances to zero net amount. | | 3 | Agent posts balanced lines into account ledgers in effective-date order. | Read posting sequence and ledger rows. | Ledger rows preserve source order and source reference. | | 4 | Agent calculates trial balance totals by account and by period. | Sum debit and credit columns in the trial balance. | Total debits equal total credits. | | 5 | Agent verifies the accounting equation after posting. | Recalculate assets, liabilities, and equity. | Assets equal liabilities plus equity. | | 6 | Agent runs targeted build or validation for posting services. | Run targeted build or ledger tests. | Build succeeds and posting assertions pass. | ## Account Type Matrix | Account Type | Normal Balance | Debit Effect | Credit Effect | Trial Balance Section | |---|---|---|---|---| | Assets | Debit | Increases asset balance | Decreases asset balance | Assets | | Liabilities | Credit | Decreases liability balance | Increases liability balance | Liabilities | | Equity | Credit | Decreases equity balance | Increases equity balance | Equity | | Revenue | Credit | Decreases revenue balance | Increases revenue balance | Income statement | | Expenses | Debit | Increases expense balance | Decreases expense balance | Income statement | ## Ledger Structure Patterns | Area | Pattern | Test | Pass | |---|---|---|---| | Chart of accounts | Agent groups accounts by major number ranges such as `1000` assets, `2000` liabilities, `3000` equity, `4000` revenue, and `5000` expenses. | Read account codes and type map. | Number range and account type align for every controlled account. | | T-account view | Agent represents each account with left-side debits and right-side credits plus running balance. | Read ledger projection. | Projection shows debit, credit, and ending balance for each account. | | General ledger | Agent stores immutable posted lines with entry id, line id, account id, amount, direction, period, source, and posting timestamp. | Read ledger schema or model. | Ledger row contains all posting trace fields. | | Trial balance | Agent summarizes opening, activity, and ending balance by account and period. | Read trial balance output. | Output supports subtotal by account type and grand totals. | | Journal validation | Agent rejects zero-line entries, mixed currencies without policy, duplicate line ids, and unbalanced amounts. | Run entry validation tests. | Invalid entries stop before posting. | ## .NET Implementation Guidance | Concern | Agent Action | |---|---| | Aggregate shape | Agent models `JournalEntry` as the posting aggregate and `JournalLine` as owned lines with immutable debit-credit direction. | | Value objects | Agent uses value objects for `AccountNumber`, `Money`, `FiscalPeriod`, and `PostingReference`. | | Validation | Agent centralizes balance, currency, and account-state checks in domain methods before persistence. | | Persistence | Agent stores posted lines in EF Core entities with explicit decimal precision and unique source references. | | Query side | Agent projects trial balance, ledger detail, and T-account views through read-side DTOs only. | | Idempotency | Agent keys imports and posting commands by source reference to prevent duplicate ledger impact. | ## Integration Hooks | Hook | Agent Action | |---|---| | EF Core | Agent maps entry headers and lines with one-to-many ownership, precision configuration, and account foreign keys. | | Domain events | Agent raises events such as `JournalEntryPosted` and `TrialBalancePrepared` after durable state change. | | CQRS patterns | Agent uses commands for create and post flows, and queries for general-ledger, T-account, and trial-balance projections. | | Repository flow | Agent keeps posting repositories aggregate-focused and keeps read models on direct query projections. | ## Verification Checklist | Check | Test | Pass | |---|---|---| | Front matter | Run `npm run frontmatter:validate`. | Command returns zero validation errors. | | STE wording | Run the repository STE violation grep on the skill file. | Scan returns zero matches. | | Balance rule | Run targeted tests for balanced and unbalanced entries. | Balanced entries post and unbalanced entries fail. | | Trial balance | Recalculate total debits and credits. | Totals match exactly within configured precision. | | Accounting equation | Recalculate assets, liabilities, and equity after posting. | Equation remains true for each verified period. | ## Common Pitfalls | Pitfall | Agent Fix | |---|---| | Account type lacks a normal balance | Agent adds explicit normal balance metadata to the account master. | | Ledger stores signed amounts without debit-credit direction | Agent stores direction and amount separately, then derives signed views. | | Trial balance skips inactive accounts with prior balances | Agent keeps zero-activity carry-forward rows where period reporting needs them. | | Posting mutates posted lines | Agent keeps posted ledger rows immutable and writes correcting entries instead. | | Import replay creates duplicate postings | Agent enforces unique source reference or idempotency key checks. | ## Outputs - Double-entry rules matrix - Chart-of-accounts guidance - General-ledger structure guidance - Trial-balance validation checklist - .NET posting integration hooks