Sec. 15(2)(d) of the CGST Act, The value of supply shall includeinterest or late fee or penalty for delayed payment of any consideration for any supply.
But on receipt-basis
Sec. 12(6) of the CGST Act, The time of supply to the extent it relates to an addition in the value of supply by way of interest, late fee or penalty for delayed payment of any consideration shall be the date on which the supplier receives such addition in value.