To secure data of the finished balance period define the General Ledger Opened field in the Administration Panel | Settings | Program Parameters | Financials | General panel. This date presents the beginning of the current fiscal year. If you open a new fiscal year it automatically means that the last one is closed. The financial report will be created and you cannot edit posts of the closed fiscal year.

The program will not allow you to create documents with the payroll date that comes before the new opening date. 

If you try to create or edit a document with a date that comes before the new opening date, the program will display an error.

Solution:

1. An incorrect period date has been entered - correct the period date on this journal entry.

2. Maybe an incorrect general ledger opening date has been entered - check it in Program parameters | Financials | General. If you want to edit this date, IN ANY CASE, consult your accounting department first!!!