Check correction deadlines for item &1 - some may be incorrect

What causes this issue?

The system was unable to create any correction deadlines (credit memo
deadlines) for this item billing plan properly. This could be because
the item billing plan is linked to the header billing plan and the end
date for the item billing plan is earlier than the end date for the
header billing plan.

How to fix this error?

Check the billing plan in question. If you still want to create
correction deadlines for this billing plan, unlink the item billing
plan from the header.

Error message extract from SAP system. Copyright SAP SE.