Cancellation of invoice in st regime & issue of gst invoice

This query is : Resolved

pritesh vaghela (Querist)
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05 January 2018 Dear Sir/Ma'am,
We are providing security services and issue monthly invoices, for the month of June 2017 we have issued invoice dated 30th June 2017 charging ST @ 15% and filed our final ST return.
We sent invoice by courier and the same was received too late by some of the clients and they refuse to pay the bills as they could not adjust the same in their system (their system might not accepting ST invoice and upgrade for GST) and asking for new invoice dated 1st July 2017 charging GST @ 18%.
We have issued new invoices to them,paid GST on the same and revised our return in ST claiming refund for the invoices cancelled.
Is it correct to do so ? Our refund claim is tenable in the eyes of the law as we have paid GST also on the new invoices issued on 1st July 2017.
We have paid tax twice on the same invoice one is ST and another in GST.
Kindly reply...
Thanks in advance..