Many times, clients call in for help with a mystery: someone or something changed the numbers from a prior period. This mystery is not a mystery at all. Without exception, someone (not something), with good intentions, modified the figures from a prior period. The only mystery is how to stop that from happening.
“Closing” the books or locking a prior period prevents access to transactions that should not be changed. It keeps prior periods in balance and allows for accurate accounting going forward.
To access this feature in QuickBooks, from the top menu simply click EDIT > PREFERENCES > select the ACCOUNTING tab on the left > click on the COMPANY PREFERENCES tab and click on the SET DATE/PASSWORD button under the Closing Date section of the window. Select a date and password and you have successfully locked the books as of the date selected.