The TypeScript framework for fintech. Double-entry bookkeeping, precision money handling, financial calculations, and audit ledgers. Zero dependencies. Built for SMB fintech developers.
npm install monetraThe TypeScript framework for fintech. Build production-ready financial applications with precision, auditability, and compliance built-in.
![Zero Dependencies]()
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🎯 Built for SMB Fintech — Invoice systems, payment processing, expense tracking, and subscription billing with ready-to-use templates.
📊 True Double-Entry Bookkeeping — GAAP-compliant ledger with journal entries, trial balance, and chart of accounts templates for SaaS, e-commerce, and small business.
🔐 Audit-Ready by Default — SHA-256 hash chain verification on every transaction. Immutable entries with void/reversal patterns. Your auditors will thank you.
💰 BigInt Precision — No floating-point surprises. Ever. Store values in minor units with up to 18 decimal places for crypto.
📦 Zero Dependencies — No supply chain risks. No transitive vulnerabilities. Just TypeScript.
``typescript
import { DoubleEntryLedger, ChartOfAccountsTemplates, Money } from "monetra";
// Set up GAAP-compliant books in 3 lines
const ledger = new DoubleEntryLedger("USD");
ledger.createAccounts(ChartOfAccountsTemplates.smallBusiness("USD"));
// Record a sale with proper accounting
ledger.post({
lines: [
{ accountId: "cash", amount: Money.fromMajor("500", "USD"), type: "debit" },
{ accountId: "sales-revenue", amount: Money.fromMajor("500", "USD"), type: "credit" },
],
metadata: { description: "Invoice #1001", reference: "INV-1001" },
});
// Verify your books balance
console.log(ledger.getTrialBalance().isBalanced); // true
`
---
Monetra is a zero-dependency TypeScript framework that provides everything you need to build financially accurate applications. From precise money handling to transaction ledgers, from loan calculations to currency conversion - Monetra offers a complete, integrated solution.
Built for financial correctness: By storing amounts in minor units (cents, satoshis, wei) as BigInt, Monetra eliminates floating-point precision errors that plague traditional approaches.
While other libraries rely on floating-point math or simple wrappers, Monetra provides a full stack architecture for the lifecycle of value: from safe storage and precise allocation to complex financial modeling and immutable audit logging.
It bridges the gap between simple e-commerce math and complex ledger systems, offering a unified, type-safe environment for building:
- Neobanks & Digital Wallets
- Billing & Invoicing Engines
- Loan & Mortgage Calculators
- Double-Entry Ledgers
Monetra is architected in three distinct layers to ensure separation of concerns while maintaining type safety across your entire financial domain.
#### Layer 1: The Core (Precision & Safety)
- Money: Immutable, integer-based monetary value object using BigInt to prevent the 0.1 + 0.2 problem.Currency
- : ISO 4217 compliance out of the box, with support for custom tokens (crypto/loyalty points).Allocation
- : GAAP-compliant splitting algorithms (Distribute value without losing cents).
#### Layer 2: The Logic (Business Intelligence)
- Financial: Standardized implementation of TVM (Time Value of Money) formulas like PMT, NPV, IRR, and Loan Amortization.Interest
- : Exact calculation of Compound vs. Simple interest with day-count conventions.Depreciation
- : Asset lifecycle management (Straight-line, Declining balance).
#### Layer 3: The Audit (Compliance & Verification)
- Ledger: Simple append-only transaction log with hash chain verification.
- DoubleEntryLedger: Full GAAP-compliant double-entry bookkeeping with accounts, journal entries, and trial balance.
- Account: Asset, liability, equity, revenue, and expense accounts with natural balance sides.
- ChartOfAccountsTemplates: Ready-made templates for small business, e-commerce, and SaaS.
- Verification: Cryptographic hashing of transaction chains to detect data tampering.
---
`bash`
pnpm add monetra
Requirements: Node.js 18+ or modern browsers with BigInt support.
---
Monetra is more than a money library - it's a complete financial framework designed to handle the full spectrum of monetary operations in modern applications.
Core Money Operations
- Integer-based storage (BigInt) eliminates floating-point errors
- ISO 4217 currency support with automatic precision handling
- Custom token definitions for cryptocurrencies (up to 18 decimals)
- Explicit rounding strategies (6 modes: HALF_UP, HALF_DOWN, HALF_EVEN, FLOOR, CEIL, TRUNCATE)
- Immutable API-all operations return new instances
Financial Mathematics
- Compound interest calculations with flexible compounding periods
- Loan amortization schedules and payment calculations
- Present/future value computations
- Net Present Value (NPV) and Internal Rate of Return (IRR)
- Depreciation methods (straight-line, declining balance)
- Bond yield calculations and leverage metrics
Transaction Ledger System
- Append-only transaction log with hash chain verification
- Double-entry bookkeeping support
- Auditable history with cryptographic integrity
- Account balance tracking and reconciliation
- Async transaction processing with event handling
Currency Management
- Multi-currency support with type-safe operations
- Currency conversion with rate management
- Historical exchange rate lookups
- MoneyBag for aggregating different currencies
- Mix-currency operation protection
Developer Experience
- Zero runtime dependencies - no supply chain risks
- Full TypeScript support with strict types
- Comprehensive error handling with custom error classes
- Extensive test coverage (>95%) and mutation testing
- Tree-shakeable modular exports
- Framework integrations (React, Vue, Node.js)
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Monetra is built for applications that require financial precision:
- Invoice & Billing Systems - Create, send, and track invoices with proper revenue recognition
- Payment Processing - Stripe/PayPal integration with fee tracking and reconciliation
- Expense Management - Employee expense reports with approval workflows
- Subscription Billing - SaaS recurring payments with deferred revenue handling
- E-commerce Platforms - Shopping carts, pricing, tax calculations, multi-currency
- Accounting Software - Ledgers, reconciliation, trial balance, financial reporting
- Cryptocurrency Apps - Wallet balances, token transfers, DeFi calculations (18 decimals)
- Banking & Neobanks - Account management, transactions, interest calculations
- Investment Platforms - Portfolio tracking, return calculations, tax reporting
Check out our Migration Guide for a smooth transition.
---
Stop worrying about floating-point errors.
`typescript
import { money, Money } from "monetra";
// Safe integer math
const price = money("19.99", "USD");
const tax = Money.fromMinor(199, "USD"); // 199 cents
const total = price.add(tax);
console.log(total.format()); // "$21.98"
`
Implement complex financial products without external formulas.
`typescript
import { money, pmt, loan } from "monetra";
// Calculate monthly mortgage payment
const payment = pmt({
principal: money("250000", "USD"), // $250k Loan
annualRate: 0.055, // 5.5% APR
years: 30,
});
// result: "$1,419.47"
// Generate the full amortization schedule
const schedule = loan({
principal: money("250000", "USD"),
rate: 0.055,
periods: 360, // 30 years * 12 months
});
console.log(Total Interest: ${schedule.totalInterest.format()});`
Real accounting with balanced entries.
`typescript
import { DoubleEntryLedger, ChartOfAccountsTemplates, Money } from "monetra";
// Initialize with SMB chart of accounts
const ledger = new DoubleEntryLedger("USD");
ledger.createAccounts(ChartOfAccountsTemplates.smallBusiness("USD"));
// Record a sale (debit AR, credit Revenue)
ledger.post({
lines: [
{ accountId: "accounts-receivable", amount: Money.fromMajor("1000", "USD"), type: "debit" },
{ accountId: "sales-revenue", amount: Money.fromMajor("1000", "USD"), type: "credit" },
],
metadata: { description: "Invoice #1001", reference: "INV-1001" },
});
// Receive payment (debit Cash, credit AR)
ledger.post({
lines: [
{ accountId: "cash", amount: Money.fromMajor("1000", "USD"), type: "debit" },
{ accountId: "accounts-receivable", amount: Money.fromMajor("1000", "USD"), type: "credit" },
],
metadata: { description: "Payment for INV-1001" },
});
// Generate trial balance
const tb = ledger.getTrialBalance();
console.log(Balanced: ${tb.isBalanced}); // true
// Verify ledger integrity (SHA-256 hash chain)
console.log(Integrity: ${ledger.verify()}); // true`
---
Full documentation is available in the docs directory:
Getting Started
- Core Concepts
- Installation & Setup
The Framework API
- Layer 1: Money & Currency
- Layer 2: Financial Math
- Layer 3: Double-Entry Ledger
- Layer 3: Simple Ledger
Guides & Best Practices
- Precise Allocation (Splitting)
- Handling Custom Tokens
- Error Handling Strategies
- Migrating from Dinero.js
- SMB Integration Examples
- Framework Examples (React, Vue, Node)
---
`bashRun the test suite
pnpm test
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See CONTRIBUTING.md for guidelines.
Check our Project Roadmap to see what we're working on.
Please review our Code of Conduct before contributing.
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Report security vulnerabilities according to our Security Policy.
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MIT - see LICENSE for details.