GST applicability on pending advance recd from client as on june17

however i have discharged GST for advance recd after July 1st

Advance Pre-GST is not considerable under GST. Advance provision is applicable on or after 1 July 17

On advances received under ST regime the provisions of ST is applicable. in your case since the advances are received in ST regime where there is no levy of ST on the activity as mentioned by you and you are forfeiting such advance now under GST regime where it is a taxable activity, in my view since the levy has attracted under ST regime and accordingly forfeiture of advance is not liable to GST.

ok sir thanku