01 November 2014
Refer Rule 6(3) - Where an assessee has issued an invoice, or received any payment, against a service to be provided which is not so provided by him either wholly or partially for any reason, [or where the amount of invoice is renegotiated due to deficient provision of service, or any terms contained in a contract] the assessee may take the credit of such excess service tax paid by him, if the assessee, (a) has refunded the payment or part thereof, so received along with the service tax payable thereon for the service to be provided by him to the person from whom it was received; (b) has issued a credit note for the value of the service tax not so provided to the person to whom such an invoice had been issued.
Going by the provision - You can raise a credit note in April - Sep 2014 period and raise a invoice in the same period. As the gross receipt and the tax payable will remain same, there is no need to revise the return.