@zenuinebit/ledger

A small double-entry ledger: balanced journal entries, account balances, trial balance, account statements, income statement and balance sheet. Amounts are integers in minor units (see @zenuinebit/money); dates are "YYYY-MM-DD". No dependencies.

import { createLedger, post, reverse, balances, trialBalance, statement, incomeStatement, balanceSheet } from "@zenuinebit/ledger";

let book = createLedger([
  { id: "cash", type: "asset" },
  { id: "capital", type: "equity" },
  { id: "sales", type: "income" },
  { id: "rent", type: "expense" },
]);

book = post(book, { id: "e1", date: "2025-01-01", memo: "Owner's capital",
  lines: [{ account: "cash", debit: 100_000 }, { account: "capital", credit: 100_000 }] });
book = post(book, { id: "e2", date: "2025-01-10", memo: "Cash sale",
  lines: [{ account: "cash", debit: 30_000 }, { account: "sales", credit: 30_000 }] });

balances(book);                       // { cash: 130000, capital: 100000, sales: 30000, rent: 0 }
trialBalance(book).balanced;          // true
incomeStatement(book, { from: "2025-01-01", asOf: "2025-01-31" });  // { income, expenses, profit }
balanceSheet(book);                   // assets = liabilities + equity + retainedProfit
statement(book, "cash");              // rows with a running balance

// Fix a mistake without erasing history: reverse it, then post the correct entry
book = post(book, reverse(book.entries[1]!, "e2r", "2025-01-11"));

Rules it enforces: every entry has at least two lines, each line has exactly one of debit or credit, total debits equal total credits, accounts exist, and entry ids are unique. Anything else throws, so a ledger built with post always balances.

Good to know

• Balances use each account's normal side: assets and expenses grow with debits; liabilities, equity and income grow with credits. A negative figure means the account is on its wrong side (an overdrawn bank, say).
• The balance sheet shows profit to date as retainedProfit, so you do not have to close the books to see it balance.
• Entries are never edited or deleted. Use reverse.

Not included: multiple currencies, storage, period closing, tax reports, and a chart of accounts for your country. Pair it with @zenuinebit/tax and @zenuinebit/invoice in your app.