Filing of Form 29B for computation of tax under MAT is not essential for processing of the return and issuing of refund. Where income was determined and refund calculated in accordance with Form 29B filed belatedly, interest on such refund could not be denied on the ground that the delay in grant of refund was attributable to the assessee since it had filed Form 29B belatedly. Interest on refund was payable to the assessee from the date of filing of the revised return of income. (AY. 2002-03)