Tax base can only be entered for Argentina, Peru, Hungary, and UAE &

What causes this issue?

The functions allowing you to change the tax base amount are only
intended for use in Peru, Argentina, Hungary, and the United Arab
Emirates. The tax base in most cases results from the posting items,
meaning the total of the posting itmes for a tax code and tax
jurisdiction gives you the tax base amount, with which the tax is
calculated. If the tax is calculated line-by-line, the tax base is
derived from the tax-relevant posting item. If the tax base amount is
entered, there is a deviation from this logic and the taxes can no
longer be declared because the tax base amounts no longer correspond to
the respective posting items, that is, the system no longer continues to
be auditable and you would have to declare the deviating entered values
to the tax authorities.

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?

Please see SAP Note 869540. This explains how you can post directly to
the tax account, for instance, for import sales/purchases tax.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.