Xero API
Cloud accounting API popular in Australia, New Zealand, and UK. Provides full double-entry accounting, invoicing, payroll, bank reconciliation, and financial reporting via REST API.
69
QuickBooks Online API
Intuit's QuickBooks Online REST API for managing accounts, invoices, customers, vendors, expenses, and financial reports for small businesses. The dominant small business accounting API in North America.
65
FreshBooks API
Cloud invoicing and accounting software API for freelancers and small businesses. Strong focus on time tracking, project-based billing, invoicing, and expense management.
63
Wave Accounting API
Free accounting software API from Wave (H&R Block owned) offering invoicing, expense tracking, and basic accounting for freelancers and very small businesses. Notably uses GraphQL.
57