For Reversal of Accrual / Deferral Document on same posting date or document date can possible.
Solution :-
1) Post your document in FBS1, here you are define reversal reason and reversal date (e.g. 01.01.2013).
2) Go for FBS2 with same document no., and click "Display Document Header (F5) (Hat symbol ), then you will get Reversal Date in edit mode, now here you first change date same as posting date or document date then save it.
3) Now go for F.81 or FB08 and reverse, it will reverse on your posting date or document date.
Regards,
Rajesh Soni