advance recd

I have received advance from client in the month of aug &SEP 17,and paid tax accordingly.and when final invoice made in mar-18, I deducted advance tax paid and balance amount paid with March return,bit forget to adjust advance in gst1 & 3b, now client's GS
TR2A Not show the amount paid in advance ,now what can I do so he will get setoff of tax amount.pls advice