As per the GST law provisions, a person who is registered under GST is required to issue an invoice/voucher at various points of transactions in the course of business.
The nature of these invoices and their requirement is explained below :-

Tax Invoice – Every registered person who is liable to charge GST on its outward supplies would be required to issue a tax invoice to its recipients and mention his GSTIN along with details of goods and services supplied by him;

Bill of Supply – A registered person who is not required to charge GST on its outward supplies , i.e., he has opted to pay GST under composition scheme or is making supplies of exempted goods or services or is making supplies to an SEZ unit or exporting under Bond, would be required to issue a bill of supply, in place of a tax invoice;

Receipt Voucher- On receipt of any advance by a registered person, he will be required to issue a receipt voucher to the recipient on the date of receipt of advance;

Refund Voucher- Where an advance has been received against which supplies have not been made by the supplier, refund voucher will be issued by the supplier to the recipient along with the details of supplies and amount refunded;

Payment Voucher- If any supply has been received from an unregistered person, then the receiver would be liable to issue a payment voucher to the supplier on the date of payment to supplier, with details of goods/services received by him;

Credit Note- Where in respect of a supply, the amount charged in the previous issued tax invoice is found to exceed the value of supply of goods or services, or the goods are returned by the recipient or the goods are found to be deficient from the amount charged, then the supplier shall issue a Credit Note to the recipient with details of excess amount charged;

Debit Note- Where in respect of a supply, the amount charged in the previous issued tax invoice is found to be less than the value of supply of goods or services, then the supplier shall issue a Debit Note to the recipient with details of additional amount to be charged.

The formats of these invoices/vouchers have been prepared considering all the relevant provisions under GST and it is advisable to display all the details as mentioned in the link above. However, the taxpayers can customize the formats as per their business requirements and convenience, keeping all the required details intact.