As per Section 31 of CGST/SGST Act a registered person shall, before or after the provision of service, but within a period of 30 days from the date of supply of service, issue a tax invoice showing description, value of goods, tax payable thereon and other prescribed particulars. For Banking and Insurance companies, this period is 45 days. For inter-state self-supplies made by bang, insurance and telecom companies, invoices can be issued before or at the time such supplier records the same in his books of account or before the expiry of the quarter during which the supply was made. Further a registered person liable to pay tax on reverse charge basis is also required to issue invoice on the date of receipt of goods or services or both.