Finance & ERP · Integration
Payhawk
Add Payhawk to your product for your customers, and give your AI agents governed access to it.
Embed a Payhawk integration so your customers can work their own company spend from inside your product instead of exporting it. Payhawk is spend management built around company cards, expenses, supplier invoices and reimbursements, and every expense carries the accounting detail finance actually cares about: a general ledger code, a tax rate, a cost centre and whatever custom expense fields that customer has configured. Those mappings differ per company, so they are configuration rather than code. Writes are idempotent, so a retry after a timeout does not book the same expense twice, and every call is logged per tenant so a posted line can be traced back to the event that created it. fastn handles per-customer authorisation, rate limits and API upkeep.
In your product
Embedded for your customers. Per-tenant auth, no per-customer code, maintained by fastn.
Let customers connect their own Payhawk account so expenses and card transactions surface in your product with their own categories and general ledger codes attached.
Create or enrich an expense from your product, including the custom expense fields a customer uses for cost centres and projects.
Read supplier invoices, reimbursements and settled payments so your product can reconcile spend without a CSV download.
Trigger your workflow when an expense is submitted, approved or exported to the customer's accounting system.
For your AI agents
Governed, audited access for the agents you build, through the MCP server.
An agent reads an expense and its receipt detail before answering an approver's question about it.
An agent codes an expense to the right general ledger account and cost centre within governed permissions, with the write idempotent and logged.
An agent reacts to an approval event and runs the next reconciliation step.
Example prompt
List card transactions from last month with no receipt attached and group them by cardholder.
Set up Payhawk in 4 steps
- 01Open the Payhawk connector from your fastn dashboard.
- 02Have each customer authenticate their own Payhawk account.
- 03Map the expense categories, general ledger codes, tax rates and custom fields your product uses, then enable actions and triggers.
- 04Call them from your product, or expose them to an agent through the MCP server.
Why teams use the Payhawk integration
What you get by embedding it with fastn instead of building it yourself.
- Ship a Payhawk integration without building it. Your customers connect their own Payhawk account inside your product and work their invoices, payments and vendors there, with no per-customer code on your side.
- Handle the part that actually costs time: financial writes must be idempotent and reconcilable, because a duplicate is an accounting problem rather than a bug. fastn owns the auth, token refresh, rate limits, pagination and breaking-change fixes, so a Payhawk update is not your on-call problem.
- One integration serves your product and your agents. The same governed Payhawk connection powers in-product features and gives AI agents scoped, audited access, so you move financial records without hand-keying them between systems without wiring it twice.
Used by these teams
Compare with
Expensify
Brex
NavanOften used alongside
Tools the same teams tend to run next to Payhawk, across other categories.
Shopify
Stripe
BigCommerce
AfterShipPayhawk integration FAQ
How do I add a Payhawk integration to my product?
Enable the Payhawk connector in your fastn dashboard, then let each customer authenticate their own Payhawk account. fastn handles the OAuth flow, token storage and refresh per tenant, so there is no Payhawk client code in your app and no per-customer branch in your codebase. Setup is 4 steps.
Do my customers each connect their own Payhawk account?
Yes. Every connection is scoped to the individual customer, so each authorises their own Payhawk account and only ever sees their own invoices, payments and vendors. That per-tenant isolation is the point of an embedded integration: you support the long tail of customer setups without maintaining an integration per customer.
Can AI agents use this Payhawk integration?
Yes. The same connection is exposed to your agents through the fastn MCP gateway, with permissions scoped per tenant and every call audited. An agent reads an expense and its receipt detail before answering an approver's question about it.
Who maintains the Payhawk integration?
fastn does. When Payhawk changes an endpoint, deprecates a field or alters its auth, the fix lands in the connector rather than in your backlog, and your customers' connections keep working.
Is the Payhawk integration safe for financial writes?
Writes are idempotent, so a retry after a timeout does not post a document twice, and every call is logged per tenant so an entry can be traced back to the event that created it. That matters more in finance than anywhere else, because a duplicate is a number somebody has to explain.
Can it handle each customer's own chart of accounts?
Yes. ERP deployments are configured to the business, so account structures, required fields and fiscal calendars differ per customer. Those are mapped per tenant as configuration, not hard-coded.
What about Payhawk rate limits during a first import?
Backfills are throttled deliberately. ERP limits are often account-wide rather than per-integration, so an unthrottled import can exhaust a customer's allowance and disrupt their other integrations.
What can I build with the Payhawk integration?
A common starting point: connect their own Payhawk account so expenses and card transactions surface in your product with their own categories and general ledger codes attached. Teams also use it for the other use cases listed above, and expose it to agents for governed reads and writes.
How much does the Payhawk integration cost?
It is included. Pricing is based on connected accounts, not on how many connectors you enable, so adding Payhawk does not change your per-connector cost. You can start free with 3 connected accounts.
Add Payhawk to your product
Start free with 3 connected accounts. No sales call required, and no per-customer integration code.