Bilnex opens its partner API: ERP vendors can build the integration themselves

To date, integrations between Bilnex and accounting software have been created for Merit Software, SmartAccounts, SimpleBooksand also Rivile. And more will be added soon, because Bilnex has opened a partner API through which ERPs or accounting softwares can integrate themselves, following their developers and their own schedule. Through Bilnex's API, ERP can offer its customers Peppol invoices, ja sending and receiving e-invoices and Digitizing PDF invoices, without having to build the solution from scratch. This could prove to be a significant competitive advantage as Europe moves towards increasingly automated billing.

The test environment is open at sandbox.bilnex.io and the test key can be obtained with one request, without an account and without prior agreement.

Bilnex is an e-invoicing and invoice management application in Estonia, Latvia and Lithuania. The Partner API is intended for software companies, not end users.

What is Bilnex Partner API?

The test environment is built so that the interface can be completed by a coding agent. Claude Code, Codex or Cursor obtains its own key, writes the code and checks on the server side whether all the required flows are actually working. The agent cannot falsely report that the work is complete, because the completion state is not defined by it, but by our checks.

There are three things that the standard API documentation doesn't provide:

You get the key yourself. One request, no authentication and you have a working key and two test companies. No need to sign anything.

The test environment behaves like the real thing. Invoices are created, rendered, and sent with the same code that runs in production. Only the outbound channels are simulated: the e-invoice reaches another test company via a real import pipeline with a PDF, just like a real invoice. The email remains in the environment and is readable from there, it does not go to anyone's real mailbox.

There is a clear “ready”. One endpoint shows twelve required checks and for each failed check also what exactly is broken and where to read it. The agent cannot mistakenly think that the work is done.

This means that an integration that used to be a sprint-long task can often be completed in a single session.

How do invoices move between ERP and Bilnex?

You can receive and send e-invoices through an interfaced ERP or accounting software. In addition, Bilnex supports both international Peppol formats and PDFs, so there is no need to assume that the counterparty is ready for e-invoices. If they are not, the invoice will still reach the recipient.

In addition to e-invoices, digitized invoices can also be directed to accounting or business software. This means that even those invoices that arrive as PDFs will, thanks to Bilnex's automatic digitization, be transferred directly to the ERP in a structured form. And for the user, there will be no difference whether the invoice arrived as an e-invoice or not.

The same interface works in Estonia, Latvia, and Lithuania, so no separate development is needed for Latvian and Lithuanian customers.

Why is this relevant today?

Regulation is moving in the same direction in all three Baltic states, just at different speeds.

In Estonia From July 1, 2025, every company registered in the commercial register as an e-invoice recipient has the right to request an e-invoice from its supplier.

In Latvia The B2G e-invoice obligation came into effect in 2025 and the B2B obligation is set for January 1, 2028. B2B e-invoices can be switched to voluntarily now.

In Lithuania B2G e-invoicing is mandatory through SABIS and B2B is still optional. The target for a nationwide B2B solution is 2028, but this has not been legislatively confirmed.

Deadlines have shifted before and may shift again. But the direction is clear, and for ERP or accounting software, it means that the question is no longer if, but when.