Enter amount or calculate tax (*)

What causes this issue?

The tax code presupposes the entry of a tax amount.

How to fix this error?

Enter the tax amount in the invoice in the field <LS>Tax</>. If
no tax amount is specified in the invoice, you can enter <LS>*</> in the
field <LS>Tax</>. In this case, the tax will be calculated automatically
from the invoice amount in accordance with the tax code.

Error message extract from SAP system. Copyright SAP SE.