Xero runs a mature REST API, secured with OAuth 2.0, covering invoices, bills, contacts, bank transactions, and reporting, with full developer documentation and a scoped-permission model so an app only gets access to what it needs. It's a real, well-documented API, which is exactly why custom integration against Xero is practical rather than theoretical, but reading the docs and building something reliable against production data are two different jobs.
The API exposes most of what you'd expect: creating and reading invoices and bills, pulling bank transactions and contacts, posting manual journals, and querying reports. It's organized around OAuth 2.0 scopes, so an integration requesting access to accounting data doesn't automatically get payroll data or the ability to void transactions, which matters if you're building something a client or a third party will trust with their books.
You get an API key and client credentials through Xero's developer portal, where the docs, a request explorer, and rate-limit details all live. Webhooks are available too, so an integration can react when an invoice gets paid or a contact changes, instead of polling the API on a schedule and hoping nothing slipped through between checks.
What the public API doesn't reach is a short, specific list: a handful of newer report customizations, certain org-level admin settings, and some UI-only configuration screens. For the rare case where a workflow genuinely needs one of those, we handle it with scripted browser automation against the Xero interface itself rather than forcing a workaround through an endpoint that was never built for the job.
Reading Xero's API docs and making one test call is a weekend project. Building something that keeps running correctly, handles a token refresh without dropping data, respects Xero's rate limits during a busy sync, and doesn't silently fail when a bank feed glitches is a different scope of work entirely. That gap is exactly why searches for xero developer and xero api documentation show up constantly alongside the raw "xero api" query.
It's also why the question usually isn't "can this be built" (with a real API like Xero's, almost everything can) but "what's the fastest, most reliable way to build it for this specific business" without reinventing a connector that already exists somewhere else.
When a business needs numbers out of Xero shaped a specific way for a dashboard, a lender, or a board report, we pull them directly through the API instead of exporting and reformatting a standard Xero report every time.
We wire Xero's webhooks into the rest of your stack so an invoice getting paid, or a contact changing, triggers the next step immediately, rather than waiting for the next scheduled check.
Describe the data you need in or out of Xero, and we'll tell you straight whether the API covers it or whether it needs a different approach.
Tell us what you're trying to move in or out of Xero and we'll scope it honestly, API call, webhook, or otherwise. Xero's API happens to be one of the better ones we work with, but the same custom-build approach applies to any system in your stack that doesn't talk to the others yet.
Let's talk →Access to the API itself doesn't carry a separate fee, but the Xero subscription behind the data you're pulling or writing still has to be active, and some higher-volume or partner-level API usage falls under Xero's developer program terms.
For anything beyond a one-off test call, yes. The API is well documented, but building a reliable, production-grade integration (correct OAuth token handling, rate-limit awareness, error recovery) is real development work, not a configuration task.
Yes. You can subscribe to events like an invoice being created, updated, or paid, so your integration reacts the moment something changes instead of polling the API repeatedly to check.
OAuth 2.0, with a scoped-permission model. An app only gets access to the specific data categories (contacts, invoices, payroll, and so on) that it explicitly requests and that the user approves during setup.
There are open-source client libraries for several programming languages that handle the low-level API calls for you, which saves time, but you (or whoever's building it) still need to write the actual integration logic on top of them.