- Notwithstanding anything contained in section 12 or section 13, the time of supply, where there is a change in the rate of tax in respect of goods or services or both, shall be determined in the following manner, namely :-

(a) in case the goods or services or both have been supplied before the change in rate of tax,-

(b) in case the goods or services or both have been supplied after the change in rate of tax,