Tutorial · GST · The law in practice

06 · Tax invoice, bill of supply, credit note, debit note

The piece of paper (or PDF) is not decoration. Wrong document type is how GSTR-1 and the customer’s credit both break. About 8 min. As of August 2026.

This tutorial explains GST the way a new founder or accounts clerk needs it, and how the same work is done in Phyntara. It is teaching, not a legal opinion. Thresholds, due dates, and late fees change when the GST Council notifies them. Your CA files. Confirm the live rule on gst.gov.in before you act on a rupee.

Tax invoice (regular GST)

If you are registered and charging GST, the document is a tax invoice. It must carry your GSTIN, the invoice number (unique, max 16 characters for the portal), date, customer name, customer GSTIN if B2B, POS, HSN/SAC, taxable value, rate, tax split, and place of business details. Digital signature / name of authorised signatory as the rules require.

B2B = buyer gave a valid 15-character GSTIN. B2C = walk-in or invalid/blank GSTIN. Phyntara classifies this; a checksum-fail GSTIN is not “close enough.”

Bill of supply

Used when you do not charge GST — composition, or wholly exempt/nil supplies in the situations the Act specifies. The customer cannot treat it as a tax invoice for ITC.

Credit note and debit note

Credit note: you already billed too much, or goods came back, or you are giving a post-supply discount that the law allows to adjust tax. Debit note: you billed too little. Both must link to the original invoice. They are not a WhatsApp “minus ₹12,000.” In GSTR-1 they live in CDNR/CDNUR, not as a silent edit of last month’s B2B row.

E-invoice (IRN)

If e-invoice applies to you (generally AATO ₹5 crore or more in any year from 2017–18, with notified exclusions), a B2B tax invoice is reported to an Invoice Registration Portal. You get an IRN and a signed QR. Until IRN exists, that PDF is not a valid tax invoice under Rule 48(4). B2C usually does not need IRN. Phyntara can request IRN when Letterhead says e-invoice is on and IRP is connected. Download the PDF again after IRN.

E-way bill

E-way is for movement of goods, not for a pure software invoice. Threshold is commonly ₹50,000 of consignment value for interstate (state rules can be tighter). If you never put goods on a lorry, leave “We move goods” off. If you do, Phyntara will offer e-way on qualifying tax invoices after IRP/e-way is connected.