Hi Karim,
Usually you use the close income statement batch after the "normal business" for the fiscal year has been registered.
It sets the "starting balance" for the P&L account to zero.
That gives you "good totals / good Balance to Date values for the P&L accounts in the new fiscal year.
Now ... even after the normal business for the previous year has been finalized there still might be some transactions to be registered (I suppose mainly in journals), for example as part of the fiscal year ending activities and the consultation of the external auditors.
This can be registered as usual.
But once the fiscal year has been closed the entries for the closed year will get a certain flag ... "prior year entry".
That's the only difference.
If the "fiscal year ending transactions" included transaction on P&L Accounts then you need to run the close income statement batch again.
If you want to make sure nobody can post in the closed year, then you need to use the "Allow Postings From" / "Allow Postings To" fields in the General Ledger Setup. The setting in the user setup can overrule this general setting.
Hope this helps
Kind Regards
Dirk