Maximum number of items in FI reached

What causes this issue?

The maximum number of items for an FI document ('001') has been
exceeded.

System Response

FI documents have a 3-digit item counter that limits the number of items
permitted per document.

How to fix this error?

For pure GL posting set header field Document Status (technical field
BSTAT) to value U (Posting in General Ledger Only).
You can use this value if the following prerequisites are met::
there are no open item managed accounts involved;
the posting is not tax relevant;
the posting relates to one company code only;

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.