What is an API in accounting software?

Definition

An API, or application programming interface, is a defined way for one piece of software to request data from another or send data to it. In accounting, APIs let ledgers, banks, payment providers, payroll, tax engines and reporting tools exchange invoices, transactions, balances and journals automatically, under permissions the customer grants, instead of through file exports and re-keying.

Also calledapplication programming interfaceaccounting APIopen API

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Lets: Systems exchange data automatically
Access: Granted and revoked by the customer
Category: ERP and general ledger

How APIs are used in accounting

Most cloud ledgers publish APIs that let approved apps read and write contacts, invoices, bills, bank transactions and journals; that is how Xero and QuickBooks support their app marketplaces. Banks provide transaction data and payment initiation through APIs, required in the UK and EU under open banking and payment services rules, which is what bank feeds and in-app payments rely on. Specialist services are delivered as APIs: tax engines such as Fonoa and Avalara return the tax for each sale, Check provides payroll for software platforms to embed, and April embeds tax filing in financial apps. For a finance team, the practical questions are what data an API exposes, how often it can be called, how access is authorised and revoked, and whether it writes back to the ledger or only reads. Unified APIs combine many ledgers behind one interface for software vendors.

Common questions

What is an accounting API?+

An API published by an accounting system that lets other software read or create records such as invoices, bills, payments and journals, with the customer's permission.

What is a unified accounting API?+

A single API that connects to many accounting systems and presents their data in one common format. Software vendors use it to integrate with dozens of ledgers without building each connection.

Is it safe to connect apps to accounting software through an API?+

It is the standard method, using authorisation that gives each app only the access it needs, without sharing passwords. Review which apps are connected and remove those no longer used.