Josh and Steve are both correct.
Typically, you want to post any adjusting entries to the last day of the prior year, use a document number that helps identify the entries as Steve suggested.
Remember you can rerun the Close Income Statement as many times as you need. For example
1. you closed the year
2. you find adjustments to make
3. open your user setup allow posting dates
4. make your new entries using last day of your fiscal year
5. reclose the income statement
6. reset your user posting dates.
Months go by and you get your auditors adjustments....just repeat the above steps 2-6
