Caution: You are deactivating extended withholding tax.

What causes this issue?

You are deactivating extended withholding tax. Note that for any given
company code, you can use either "standard" or extended withholding
tax. However, you can only change from "standard" to extended
withholding tax and not vice versa. Changing to extended withholding
tax involves converting datasets.
Deactivating extended withholding tax leads to large inconsistencies in
the datasets.

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?

Ensure that you really do want to deactivate extended withholding tax.
Consult an SAP consultant before coming to a final decision.

Error message extract from SAP system. Copyright SAP SE.