Locking Posting Periods 
The following procedure explains how to lock a posting period and thus prevent the future submission of any updates in that period. You perform this task after you have completed the year-end closing process.
Prerequisites
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In the Authorizations window, the Change Period Status authorization under
Administration 
System Initialization Posting Period
has been set to No Authorization for users who should not be allowed to lock or unlock posting periods and to Full Authorization for users who need to perform this procedure. -
The year-end closing process has been completed. For more information, see the how-to guide Tips for Year-End Closing in the documentation area of SAP Business One Customer Portal at http://service.sap.com/smb/sbocustomer/howtoguides88.
Procedure
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From the SAP Business One Main Menu, choose
Administration System Initialization Posting Periods . -
Click the
(Link Arrow) icon of the period you want to lock.The Posting Period window appears.
-
In the Period Status field, change the value to Locked.
-
Choose Update and choose OK.
Result
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From now on, it is impossible to submit any updates against the locked period. If you need to do this, you must first unlock the posting period.
-
The application has registered the locking action in a log file, together with the date and the name of the user who performed the action. To see this log file, open the Posting Period window of the period in question and, from the menu bar, choose
Tools Change Log... .