- Daybook transactions
- VAT models
- Reminder schemes
API V1 Documentation
On this page and its subpages you will find anything you need to know to use our API.
Notice about versions
This page and subpages describe our V1 API (the one found on https://api.billysbilling.dk/v1). All organizations that belong to the V1 system MUST use the V1 API. V1 organizations are logged in on login.billysbilling.dk.
All organizations that belong to the V2 systems MUST use the V2 API (the one found on https://api.billysbilling.com/v2). V2 organizations are logged in on app.billysbilling.com or app.billysbilling.dk. See V2 API documentation.
Before using our API you must read and accept our API Terms.
The API is based on REST principles, which makes it very easy to write and test applications. You can use any HTTP client in your favorite programming language to communicate with the API. You can also point your browser to the API’s base url and navigate the API to see how it works.
The API’s base url is:
Your API can use the HTTP verbs (GET, POST, PUT and DELETE) to manipulate resources. You can use GET to list a collection of resources or to get a specific resource. You can use POST and PUT to respectively create and update resources. And you can use DELETE to delete resources.
All data is transferred to and from the API as JSON.
Responses, status codes and errors
All responses from the API contain a JSON document. The JSON document will have a
success boolean element, where
true means that the request was accepted and properly handled, while
false means that something went wrong.
If the request produced an error, it will be returned as as string in the
error element. There will also be a URL where you can find help for this error in the
Also check out our page with programming examples.
You can see all available REST resources in the left menu.
This resource collection contains all of the organization’s invoices.
You can POST to the resource to create new invoices.
Contacts includes both customers and suppliers. A contact can have both invoice receivables and invoice payables.
To create an invoice, you need to create a contact first.
This resource collection contains all the payments made to invoices.
A payment can pay for more than one invoice.
Products are used in invoice lines. They determine which account revenue from invoice lines is coded to. They also determine which VAT model that is used to calculate VAT for invoice lines.
Daybook transactions are collections of postings to particular accounts.
This resource collection contains all of the accounts in the organization’s chart of accounts.
Accounts can currently only be created/updated via the web interface. The API only provides read access to accounts.
This resource collection contains all of the organization’s VAT models.
VAT models are used by products to calculate VAT on invoice lines.
VAT models can currently only be created/updated via the web interface. The API only provides read access to VAT models.
This resource collection contains all of the organization’s reminder schemes.
Reminder schemes handle automatic sending of reminders for overdue invoices.
Reminder schemes can currently only be created/updated via the web interface. The API only provides read access to reminder schemes.
Organization is the owner of the accounting.