Exceeds final account assignment quantity

What causes this issue?

During invoice entry you want to post a quantity to an account
assignment item which has a <DS:DE.AA_FINAL_IND>final account assignment
indicator</> in the purchase order to which it is referenced.
When determining the <DS:DE.AA_OPEN_QTY>open quantity</> that you are
currently allowed to post to the item with a final account assignment,
the system calculates the difference between the <DS:DE.AA_FINAL_QTY>
final account assignment quantity</> and the invoice quantities that
have already been posted to the account assignment item.
When calculating the quantity difference, the system only includes
quantities from posted incoming invoices, and does not take parked
invoice quantities into account. However, you can specify in Customizing
for <ZK>Public Sector Management</> that the system should take into
account invoices with the status <ZK>parked as complete</> and <ZK>
parked released</> when calculating the final account assignment
quantity. Then the system also includes invoices with those two statuses
when calculating the open quantity.

System Response

This is an error message. You cannot post any further invoice quantities
to this account assignment item.

How to fix this error?

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.