Tax Invoice and other such instruments in GST :
Goods
The time for issuing invoice is depend on the supply of goods or service. A registered person supplying taxable goods shall, before or at the time of removal of goods (where supply involves movement of goods) or delivery or making available thereof to the recipient, issue a tax invoice showing the description, quantity and value of goods, the tax charged thereon and such other particulars has been prescribed in the Invoice Rules.
Services
A registered person supplying taxable services shall, before or after the provision of service but within a prescribed period, issue a tax invoice, showing the description, value, tax charged thereon and such other particulars as has been prescribed in the Invoice Rules.
Thus it can be seen that in case of goods, an invoice has to be issued before or at the time of supply. In case of services, however, invoice has to be issued before or after provision of services. If the invoice is issued after provision of service, it has to be done within the specified period of 30 days from the date of supply of service, as per invoice rules