Go to Accounting > General Ledger > Close/Open Month.
Click Open Closed Month. The Current Accounting Month field reverts to the previous month (which is now the current open month).
You can go as far back as you want, one month at a time.
After you have finished making changes, close the month (or months) you opened, so the system is back in the current month.
Note(s):
To open a closed month, go to Accounting > General Ledger > Close/Open Month.
If you have permission to post in closed months, you do not need to fully re-open a closed month.