Table &1: W/tax type &2 is posted on invoice posting in country &3

What causes this issue?

In your system settings, you selected the option "Posting on invoice"
for extended withholding tax type &V2&. In classic withholding tax
however, posting is only possible on payment.

System Response

The effect of this setting is that documents that were posted to
extended withholding tax before the changeover are treated differently
after the changeover. The problem is explained in the following
example:
An invoice is posted before the withholding tax changeover. Since only
posting on payment is possible in classic withholding tax, no
withholding tax is posted when the invoice is entered. If the system is
the changed over to extended withholding tax, and the conversion
results in this invoice using a different withholding tax type after
the conversion, (a type that uses the option "posting on invoice"), no
withholding tax is posted for this invoice at the time of payment
either.

How to fix this error?

Check the following system settings and adjust them if required:
Customizing for extended withholding tax: Time of posting for
withholding tax type &V2&.
Assignment of withholding tax types/codes (second step in conversion
run).

Error message extract from SAP system. Copyright SAP SE.