Provisional Assessment :
Where the taxable person is unable to determine the value of goods or services or both or determine the rate of tax applicable thereto, he may request the proper officer in writing giving reasons for payment of tax on a provisional basis and the proper officer shall pass an order, within a period not later than ninety days from the date of receipt of such request, allowing payment of tax on provisional basis at such rate or on such value as may be specified by him – section 60(1) of CGST Act.
Bond with security – The payment of tax on provisional basis may be allowed, if the taxable person executes a bond in such form as may be prescribed, and with such surety or security as the proper officer may deem fit, binding the taxable person for payment of the difference between the amount of tax as may be finally assessed and the amount of tax provisionally assessed – section 60(2) of CGST Act.
Final assessment within six months – The proper officer shall, within a period not exceeding six months from the date of the communication of the order under section 60(1), pass the final assessment order after taking into account such information as may be required for finalizing the assessment.
The period specified in this sub-section may, on sufficient cause being shown and for reasons to be recorded in writing, be extended by the Joint/Additional Commissioner for a further period not exceeding six months and by the Commissioner for such further period not exceeding four years – section 60(3) of CGST Act.
Interest payable if tax payable after final assessment is more than tax earlier paid – The registered person shall be liable to pay interest on any tax payable on the supply of goods or services or both under provisional assessment but not paid on the due date specified under section 39(7) of CGST Act or the rules
made thereunder, at the rate specified under section 50(1) of CGST Act, from the first day after the due date of payment of tax in respect of the said supply of goods or services or both till the date of actual payment, whether such amount is paid before or after the issuance of order for final assessment – section 60(4) of CGST Act.
Refund if tax payable was less – Where the taxable person is entitled to a refund consequent to the order for final assessment under section 60(3), interest shall be paid on such refund as provided in section 60(5). Such refund is subject to doctrine of unjust enrichment [section 54(8)] – section 60(5) of CGST Act.