The total of the partial amounts varies from the invoice amount by & &

What causes this issue?

The total of the partial amounts entered does not match the (total)
gross invoice amount.

System Response

You cannot continue processing this document.

How to fix this error?

Navigate to the header data screen, if necessary, and, in the
'Withholding tax' area of the screen, select the pushbutton to split
the invoice amount.
Check the partial amounts entered and adjust them accordingly, so that
the total of the partial amounts matches the gross invoice amount
entered.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.