There is no exemption. Even for advance receipt, the slab will be 5%.
GST is on billing or receipt whichever is earlier.
If you raised invoice first, then pay GST as per Invoice.
If you received money in advance then charge GST as per advance.
However only difference is that your customer will not get input in case of advance payment. He will get input only once invoice is issued to him, return is filed and tax paid by you.