Once all of the general ledger transactions have been posted to any given period, the trial balance and other financial statement reports are typically run. However, these reports can be printed at any time during or after a period, so running them at the end of each period is not required.
Year end processing typically consists of the following procedures:
Year end journal entries (See 28521 JOURNAL ENTRY).
Print general ledger report, trial balance and other financial statements.
The year end purge can be run anytime after the actual year end. However, financial statements cannot be printed for the "next" year until the prior year's year-end purge has been performed. Therefore it is recommended that the year-end purge be performed as soon as possible. Keep in mind that you can make adjusting journal entries to last year and also print all reports for last year's information as well, so by performing the year end purge you are not restricted in any way.
Do not run the month end purge and the year end purge at the end of the year. Run only the year end purge.