Acumulus API voor uw boekhouding

Using the API to connect

The Acumulus API allows you to interact with our system programmatically from your own application. By using the API you interact with resources such as invoices, expenses and information about contacts.

We attempt to conform to the RESTful design principles. The API accepts XML and returns either JSON, XML or raw data like PDF-files.


The API Authentication is implemented as HTTP Basic Authentication over TLS (HTTPS). Your API login credentials can be, but should not be the same as the credentials you use to access the web interface. We strongly advise to setup an additional user from the webinterface specifically to access the API. In most cases a user of the API-type is sufficient for interaction with the resources and endpoints.


If you are having trouble executing a request via the API you can try to host the XML-code you want to submit on a secure website and invoke the request using a browser. Please use the xmlfile approach from your browser to directly see the response given.

Alternatively be sure to use the emailonerror and emailonwarning XML-nodes in every generic request.

If you can get no connection to the API at all you might be using an older and unsupported encryption protocol. Please note that TLS version 1.2 or higher is mandatory.


@SIEL we have asked Buro Rader to help out implementing various plugins for external software like webshops. The modules and plugins all share a common codebase/library when interacting with our API.

We refer to this library as libAcumulus. The library has been written in PHP and is licensed under the GNU GPLv3 Open Source license. It has seen several development cycles allowing it to mature and deal with common pitfalls and accouting challenges.

Feel free to download libAcumulus from Github and use it to get a head start when implementing more complex and feature-rich applications.