Madam,
According to Section 12 (3) of CGST Act, 2017-
" In case of supplies in respect of which tax is paid or liable to be paid on reverse charge basis, the time of supply shall be the earliest of the following dates, namely:-
(a) the date of the receipt of goods; or
(b) the date of payment as entered in the books of account of the recipient or the date on which the payment is debited in his bank account, whichever is earlier; or
(c) the date immediately following thirty days from the date of issue of invoice or any other document, by whatever name called, in lieu thereof by the supplier:
Provided that where it is not possible to determine the time of supply under clause (a) or clause (b) or clause (c), the time of supply shall be the date of entry in the books of account of the recipient of supply."
Therefore you have to pay the tax on or before 10.9.2017. If you pay now you have to pay interest for delayed payment.
Notification No. 38/2017 – Central Tax (Rate) dated 13.10.2017 amends Notification No.8/2017- Central Tax (Rate), dated the 28th June, 2017. This amendment is prospective in effect. Invoices issued prior to this date are liable to payment of tax under reverse charge if required by law.