Tax number category &1 already contains an entry

What causes this issue?

The tax number table already contains an entry for tax number category
&V1& with this business partner. Only one entry per tax number category
is permitted in the tax number table.

System Response

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?

Delete the entry or change the tax number category of the entry.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.