Choose a document type with internal number assignment.

What causes this issue?

For the fast entry of incoming payments and for recurring entries,
only document types which work with internal number assignment are
provided.

System Response

The entered document type is rejected because the corresponding
document numbers are assigned externally.

How to fix this error?

Enter a document type which uses a number range with internal number
assignment.

Error message extract from SAP system. Copyright SAP SE.