How to lock a period after filing
After you file a return or close a year, lock the period: nothing dated in it can be posted any more.
Steps
Open Lock periods
Choose Settings, then Lock periods.
Add the period
Choose Add period and enter its last day; add a comment such as the return it was filed for.
Close it
A closed period is enforced: postings dated on or before its end are refused.
Correct in the open period
A later correction posts to the open period as an adjustment, leaving the filed figures as they were.