You can enter adjustments to your previous year and close those prior year adjustments to retained earnings as many times as you need during the current fiscal year. You can only close the General Ledger fiscal year after you have closed your prior year adjustments and when you are in the last period of your current fiscal year. If you are not currently in the last period of your fiscal year, then the Close Fiscal Year task only closes prior year adjustments. It does not close your fiscal year.
See the link below for more information on closing a prior year adjustment to retained earnings.
DocLink: How do I close prior year adjustments to retained earnings?