You cannot enter a tax amount when 'Calculate tax' is selected

What causes this issue?

You have entered a <LS>Tax amount</> in addition to selecting
<LS>Calculate tax</>. This is contradictory.

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 check if the tax amount is actually indicated in the invoice.
If it is, deselect <LS>Calculate tax</>.
If not, delete the entry in the <LS>Tax amount</> field.

Error message extract from SAP system. Copyright SAP SE.