UNIT4 Message Expresse is a proxy that allows different providers to hook up and facilitate the sending of documents, for example tax declarations.
This document is meant for technical readers, as it describes the API and workflows.
For a more general explanation, please contact your account manager at UNIT4. He will provide additional information.

To call/access the API an SSL client certificate needs to be used for identification.
The public part of the certificate needs to be known at UNIT4 Message Expresse beforehand.
Send us the public part of your certificate. We do prefer two certificates, one for production and one for acceptance environment.
The certificate is used as client verification and has to be used in all API-Calls towards MessageExpresse.

Only client defined applications can post documents towards Message Expresse. The only application that has this propertie is Unit4 Fiscaal Gemak.
Before a document can get posted to Message Expresse, tenant settings should be send to bind a FiscaalGemak tenant to your application tenant.
For verification that the two tenants belong to the same person, the user that uses FiscaalGemak enters his/her credentials in the UI of FG, FG does a POST to tenant settings and depending on the type of provider ME/FG will test if these credentials are correct. For each provider there should be some kind of security check in place to make sure that the user can access the provider.
ME does not store passwords, only an ID that will be used as the tenantid.
How the check takes place depends on the provider that wants to connect ie username/password, secret passphrase, two factor, etc.

The following flow covers the basic two-step process of ME.


Normal process, no special steps initiated.

What follows is a normal, happy process flow. Providers are hooked up.

Forced approval

Cancel process