reverse charge

For reverse charge liability arises on the date of payment to the vendor. If the payment is not made to the vendor, then on 31st/61st day for goods/services respectively from the date of invoice as per the provisions of time of supply. 

In your case, if the payment is also made then liability arises. If no payment is made and if the above dates from the date of invoice is falling after 12.10.17 then there is no GST liability.