Back to changelog

Invoicing Infrastructure

Release
v2026.5.2
AprAprAprMayMayMay
8new
2improved

Use Expensicat as the invoicing engine behind your product

Building something that needs to send real invoices? A marketplace paying out sellers, a SaaS billing flow, an AI agent handling billing for its user — you can now plug Expensicat in as the engine behind it, and your customers never have to leave your product.

You don't have to rebuild the hard parts either. Sequential legal numbering, EU-compliant formats (Factur-X, ZUGFeRD, XRechnung, EN 16931, Peppol UBL), the audit trail, automatic reminders, and reconciliation with your bank — it all comes along for the ride.

Four things that make this production-ready

We spent the time on the small details that separate a fun-to-demo invoice API from one you can actually bet your billing on:

  • API keys you can scope — issue one per integration, restrict it to just the resources it needs
  • Safe to retry — if your network blips, sending the same request again brings back the same invoice (no awkward duplicates for your customer)
  • Your IDs stay yours — pass the customer and invoice IDs you already use in your system, and we'll make sure nothing gets created twice against them
  • Preview before you commit — run the full calculation, see the exact document your customer will see, and only persist it when you say go

One call from draft to issued

A single request takes a draft and turns it into a finalized, sendable invoice. The snapshot is locked, the next sequential number is assigned, and the issued files are generated — both the PDF your customer reads and the structured file their accounting system reads.

Need the files later? Download the PDF, the structured file, or a bundle of both, any time.

  • APISend invoices to your customers from your own product, app, or AI agent. Expensicat handles the document, the format, and the legal bits.
  • APICreate API keys, and lock each one to just the things it should be allowed to do.
  • APISafe to retry. If your request times out or your network blips, sending it again won't create a duplicate invoice.
  • APIBring your own IDs for customers and invoices — Expensicat won't let you accidentally create duplicates.
  • APIPreview the exact invoice your customer will see before you issue it. Nothing is saved until you say so.
  • APIIssue a finalized invoice in a single call — locked, numbered, and ready to download.
  • APIDownload issued invoices as a PDF, the structured file accounting systems expect, or both as a bundle.
  • APICreate reusable invoice templates over the API.
  • SDKThe Expensicat SDK now covers all of the above: preview, finalize, downloads, templates.
  • ComplianceInvoices issued through the API run through the same European compliance checks as the ones you create in the dashboard.