You can prevent the closure of a General Ledger accounting period if the accounting period for any of the corresponding subledgers is still open, or if incomplete accounting entries or transactions exist for the period.
This can help ensure an effective period close process that validates all transactions are complete and aren't held up during the close. To enable this feature, you need to set the relevant option on the Specify Ledger Options page for each primary ledger. The option is called Prevent General Ledger Period Closure When Open Subledger Periods Exist and it is located in the Period Close section. You can also specify which subledgers to include or exclude from the validation, except for Assets, which is automatically excluded by default. References:
How to Prevent a General Ledger Period from Closing When Open Subledger Periods Exist Period Close Components Review: Prevent General Ledger Period Closure When Open Subledger Periods Exist