after the all checking setting just go to open your posting period if closed, then reverse the entry and then post like this
for example
Now post a new document with Doc date 31.03.2010, Posting date 31.12.2009 and enter the period manually as 15, then it posts the transaction to the special period.
Since
01-2010 is the 13th period for the calendar year 2009.
02-2010 is the 14th period for the calendar year 2009
03-2010 is the 15th period for the calendar year 2009
04-2010 is the 16th period for the calendar year 2009
So your audit entry related to 03-2010, means it should be posted with special period 15 only.
Note: No document will be posted automatically to the special periods, unless you enter the special period in the period field manually during document entry.
This will resolve your issue.
nagendra