Table &1: Base amounts for w/tax type &2 in country &3 inconsistent

What causes this issue?

One or more of the withholding tax codes that you use in classic
withholding tax is reflected in withholding tax type &V2& after the
changeover. For the classic withholding tax code, the net amount was
used as the base amount, but for withholding tax type &V3& in country
&V3&, a different setting is used.

System Response

The withholding tax base amount would be determined differently after
the changeover.

How to fix this error?

Check the following system settings and change them if necessary:
Customizing for extended withholding tax: Definition of withholding tax
types: Base amount
Assignment of withholding tax types/codes (second step in conversion
run).

Error message extract from SAP system. Copyright SAP SE.