Document type & not defined

What causes this issue?

Financial Accounting service: document type "&v1&" was not found in the
document type table. There are two possible causes:
document type "&v1&" has not been set up in FI customizing
document type is supplied incorrectly from the calling application

System Response

System error.

How to fix this error?

There are two possible measures:
set up document type "&v1&" in FI customizing
system error within the calling application - get in contact with the
SAP Hotline Service.

Error message extract from SAP system. Copyright SAP SE.