Terms of payment & are not defined.

What causes this issue?

Payment Terms &V1& are invalid.

System Response

Error message. The system checks the payment terms you entered against
those defined in Table T052. Payment terms &V1& are not a valid entry.
Further document processing is not allowed.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Check your entry.
Valid payment terms should be maintained in the vendor or customer
master record and will then be automatically defaulted to the LIA.
Payment terms may still be entered in a LIA transaction, but the entry
must exist in the terms of Payment Table (T052). Possible entries may
be displayed by positioning the cursor on the 'Terms of payment' field
in the document and selecting F4.
Enter valid payment terms or maintain Table T052.

Error message extract from SAP system. Copyright SAP SE.