Section 13 - Time of supply of services of CGST ACT, 2017

        13. (1) The liability to pay tax on services shall arise at the time of supply, as determined
in accordance with the provisions of this section.
             (2) The time of supply of services shall be the earliest of the following dates, namely:—
                  (a) the date of issue of invoice by the supplier, if the invoice is issued within the
period prescribed under sub-section (2) of section 31 or the date of receipt of payment,
whichever is earlier; or
                  (b) the date of provision of service, if the invoice is not issued within the period
prescribed under sub-section (2) of section 31 or the date of receipt of payment,
whichever is earlier; or
                  (c) the date on which the recipient shows the receipt of services in his books of
account, in a case where the provisions of clause (a) or clause (b) do not apply:
           Provided that where the supplier of taxable service receives an amount up to one
thousand rupees in excess of the amount indicated in the tax invoice, the time of
supply to the extent of such excess amount shall, at the option of the said supplier, be
the date of issue of invoice relating to such excess amount.
            Explanation.––For the purposes of clauses (a) and (b)––

                (i) the supply shall be deemed to have been made to the extent it is covered
by the invoice or, as the case may be, the payment;
                (ii) “the date of receipt of payment” shall be the date on which the payment
is entered in the books of account of the supplier or the date on which the
payment is credited to his bank account, whichever is earlier.
      (3) In case of supplies in respect of which tax is paid or liable to be paid on reverse
charge basis, the time of supply shall be the earlier of the following dates, namely:––
              (a) the date of payment as entered in the books of account of the recipient or the
date on which the payment is debited in his bank account, whichever is earlier; or
              (b) the date immediately following sixty days from the date of issue of invoice or
any other document, by whatever name called, in lieu thereof by the supplier:
    Provided that where it is not possible to determine the time of supply under
clause (a) or clause (b), the time of supply shall be the date of entry in the books of
account of the recipient of supply:
   Provided further that in case of supply by associated enterprises, where the
supplier of service is located outside India, the time of supply shall be the date of entry
in the books of account of the recipient of supply or the date of payment, whichever is
earlier.
  (4) In case of supply of vouchers by a supplier, the time of supply shall be––
              (a) the date of issue of voucher, if the supply is identifiable at that point; or
              (b) the date of redemption of voucher, in all other cases.
  (5) Where it is not possible to determine the time of supply under the provisions of
sub-section (2) or sub-section (3) or sub-section (4), the time of supply shall––
             (a) in a case where a periodical return has to be filed, be the date on which such
return is to be filed; or
            (b) in any other case, be the date on which the tax is paid.
  (6) 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.