Diagnosis
You cannot save an entry with the error code 03 (Incoming 0%Operations) if the old code is not an output tax code and the newcode is not an input tax code.
Error code 03 indicates that you want to change the default target taxcode of an incoming 0% invoice, which is linked to an outgoing 0%invoice. Thus, the old code has to be the tax code of the outgoing 0%invoice and the new code has to be target tax code of the linkedincoming invoice.

System Response
The system does not save the entry.

Procedure
Enter an output tax code in the Old Code field and an input taxcode in the New Code field.