Deletion not possible: Goods receipt/invoice receipt not yet reversed

What causes this issue?

If Funds Management (FM) is active, purchase order items cannot be
deleted if goods receipts (GR) and/or invoice receipts (IR) exist.

System Response

You can only delete purchase order items when the corresponding
follow-on documents (IR and/or GR) have been reversed in both Materials
Management (MM) and Financial Accounting (FI).
In the current case, the GR balance and the IR balance are actual (both
in the transaction currency).

How to fix this error?

This message can be issued as an error, warning, as information or
completely surpressed. The default value is E (error).
Note that balancing problems between MM, FI, FM, the budgetary ledger,
and SPL documents could occur if the deletion of purchase order items is
allowed.
When archiving object MM_EKKO, FM is not updated and the message is not
regarded. Only the MM data is updated. As such, the Customizing for
this message does not affect the setting of the deletion indicator by
the archiving program <LS>Write Program Archiving Purchasing Documents
</>(RM06EW30).
If you want, you can implement user exit EXIT_SAOLFMOI_009 to skip the
deletion of the purchase order without regarding the user ID.

Procedure for System Administrators

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.