Hello BS Reddy,
Thanks for your reply.
I just checked my requirements types again, actually for returns the requirements types is assigned as 011 as well as Req. Class also 011.
So, as you mentioned above the rquirements class should have the account assignment category as M, I assigned the requiremets type KEB (it has the category-M) and now the accounting document is generated successfully.
Thanks a lot for your hint that helpmed so much......
Thanks,
Sreehari.