Unable to Update Tax Registration Number in Customer Master

While attempting to update the Tax Registration Number (TRN) in the Customer Master under ‘Default Tax Registration Number’, we encountered the following error:

“This Tax Registration Number is already in use for Party Type: Third Party Site, Party Name: XXXXX, and Party Site Name: XXXX for the same Period.”

Upon further review, we found that the TRN is already associated with a Supplier record, and it's a valid entry. Hence, removing it from the Supplier Master is not a feasible option.

We referred to several Metalink notes, which recommended the following steps:

• Enable ‘Allow Duplicate Tax Registration Numbers’ at the