If you request fails for some reason, VatZen API will return non-200 HTTP code as well as JSON response which will contain details about the error occurred.
Here's the format of error object, which is returned by the API:
Here's the example of the error object:
"message": "You did not provide proper API key, please check documentation"
In the table below, you can find all the possible errors that VatZen API can return: