Want to revised mvat returns 2nd time for c forms.

Dear Sir

I have already revised MVAT Returns once u/s. 20(4), Now new error came to light, OMS purchases part was wrongly added in Tax Free, due to this Department is not issuing C-Forms - as total amount of C-Forms is more than what was mentioned in Form 231.

Now I want to Revise returns again, otherwise we will not get C-Forms. As I have already revised returns once, second time is not allowed, please guide me what to do, as obtaining C-forms is necessary otherwise suppleir will debit that amount to us. Please Guide.