You can store your own data at Billomat entities by using the so called “customfield”. For example this could be the primary key from your system to synchronize Billomat data with the data in your database.
GET /api/clients/{id}/customfield
<?xml version="1.0" encoding="UTF-8"?> <client> <id type="integer">{id}</id> <customfield>foo</customfield> </client>
PUT /api/clients/{id}/customfield
<client> <customfield>bar</customfield> </client>
<?xml version="1.0" encoding="UTF-8"?> <client> <id type="integer">{id}</id> <customfield>bar</customfield> </client>
To find entries with specific meta-data associated, the search parameter “customfield” can be used.
PUT /api/clients/?customfield={search_string}