All previously entered withholding tax and splitting data will be lost

What causes this issue?

The supplier number, company code or posting date has been changed.
Since withholding tax data is dependent on this data, the system must
delete all the withholding tax and splitting data entered so far and
re-determine the possible withholding tax categories and indicators.

System Response

All withholding tax and splitting data entered so far is deleted.
The necessary withholding tax categories and their categories are
re-determined. The splitting table is reset to one split amount (the
gross invoice amount).

How to fix this error?

If you have to make manual entries for the withholding tax base, the
amounts or tax already withheld, process the header data screen. Go to
this again if you have already exited it.
If you want to split the invoice amount, you must go from the header
data screen to the splitting screen and maintain the splitting data
again.

Error message extract from SAP system. Copyright SAP SE.