Tax Invoice
A tax invoice is the main document for supporting an input tax claim.
You must keep the tax invoices issued to your customers, and those given to you by your suppliers, for at least five years. You do not need to submit these tax invoices with your GST returns.
When to Issue a Tax Invoice
A tax invoice must be issued when your customer is GST registered. Your customer needs to keep this tax invoice as a supporting document to claim input tax on his standard-rated purchases. In general, a tax invoice should be issued within 30 days from the time of supply .
A tax invoice need not be issued for zero-rated supplies , exempt supplies and deemed supplies or to a non-GST registered customer.
Your tax invoice must also provide details on exempt, zero-rated, or other supplies, if applicable. The gross amount payable for each type of supply must also be separately stated.