After you've completed your month-end tasks, you should lock that period using the Lock Periods feature. This will prevent anyone from inadvertently making an entry in a period in which you don’t want new entries. To do this:
Go to the Setup menu and choose Preferences. The Preferences window appears.
Click the Security tab.
Select the Lock Periods: Disallow Entries Prior to option, and select the relevant date. This selection places a temporary lock on the date you select and the period before it.
Need to make a change in a locked period? If you need to make an entry in a locked period at a later time—for example, you locked 31st of May, and now want to make an entry in April— you can unlock that date in the Preferences window. Note that your user role needs to be have the permission to change preferences.