There are various reasons why issuing invoice under GST is extremely important.

1. Proof of Supply
Invoice acts as a proof of supply of goods and services by a registered person under GST. It forms the basis on which a supplier can demand payment from the buyer of such goods and services.

2. Claiming ITC
Invoice is important under GST as it is a document based on which the recipient claims ITC for the inputs purchased by him. This means that a recipient cannot claim ITC till the time he does not have a tax invoice or a debit note with him.

3. Time of Supply
Invoice is issued at the time of the supply of goods or services. GST is charged at the time of supply of goods or services. Further, invoice is issued at the time of supply of goods or services. It is one of the factors that indicates time of supply. This is because time of supply is nothing but the date on which the invoice is issued or the date on which the payment is received, whichever is earlier.

Read More: Mandatory Fields a GST Invoice Should Have