Purchase Invoice Format: Required Fields & GST Guide

Indian factory accounts team reviewing purchase invoices and GST paperwork at a desk

TL;DR: A purchase invoice is the seller’s tax invoice from your side of the transaction, the document that lets you claim GST input tax credit on what you bought. Get the required fields wrong and the credit claim can be rejected, not just the paperwork.

For a manufacturer buying raw material every week, purchase invoices aren’t a filing formality. Every missing GSTIN or mismatched HSN code is credit you can’t claim back, and at volume, that adds up fast.

What Is a Purchase Invoice?

A purchase invoice is simply the tax invoice your supplier issues you, recorded from the buyer’s side. It’s the same document, a sale from the seller’s perspective and a purchase from yours, and it’s your proof of the transaction for both accounting and GST purposes.

It’s what supports your input tax credit claim. Without a GST-compliant purchase invoice on file, matched correctly in your returns, the tax you paid on that purchase isn’t recoverable.

The format is fixed by law. Getting every required field right, every time, is where manual systems slip.

Purchase Invoice Format: Required Fields

Under Rule 46 of the CGST Rules, a tax invoice, and therefore the purchase invoice you receive, must carry a fixed set of fields. Use this as your format checklist:

Invoice identity: a consecutive serial number, unique for the financial year and no more than sixteen characters, plus the date of issue.
Supplier and buyer details: name, address, and GSTIN of the supplier, and name, address, and GSTIN or UIN of the recipient if registered.
Goods details: HSN code, description of goods, quantity, and unit of measure for each line item.
Value and tax: taxable value, applicable rate and amount of CGST, SGST, IGST, or cess, total invoice value, and signature.

Indian factory worker operating a digital touchscreen control panel on a machine

Common Purchase Invoice Mistakes to Avoid

Most rejected input tax credit claims trace back to one of five recurring errors:

Incorrect or missing GSTIN: a single wrong digit means the invoice won’t match on the GST portal, and the credit gets held up or rejected.
Wrong HSN code: misclassifying an item changes the applicable tax rate and can flag the return for scrutiny.
CGST/SGST vs IGST mismatch: charging intrastate tax on an interstate purchase, or vice versa, is one of the most common purchase-side errors.
Missing signature or authentication: a tax invoice without a valid signature or digital signature isn’t compliant, even if every other field is correct.
Confusing it with a proforma invoice: a proforma has no tax liability and can’t be used to claim input tax credit, only a proper tax invoice can.

Stop chasing suppliers for invoice corrections

TranZact’s AI Invoice step matches purchase invoices against your PO and GRN as they come in, catching field errors before they turn into a rejected credit claim.

Book a free demo →

Purchase Invoice vs Proforma Invoice vs Bill of Supply

A purchase invoice is the actual tax invoice for a completed sale, carrying full GST liability and enabling input tax credit.
A proforma invoice is a preliminary quote sent before the sale is finalized. It has no tax liability and can’t be used for credit claims.
A bill of supply is issued instead of a tax invoice by suppliers who can’t charge GST, such as those under the composition scheme, or for exempt goods.
Only the tax invoice, your purchase invoice, supports an input tax credit claim. The other two don’t.
If a supplier sends a proforma instead of a tax invoice for a completed purchase, that’s a compliance gap worth flagging before you record it.

Automating Purchase Invoices with TranZact

TranZact’s AI Invoice step sits inside the same flow as your PO and GRN tracking, so a purchase invoice gets checked against what was ordered and what actually arrived, not re-keyed from scratch into a separate accounting entry.

If you run accounts in Tally or Zoho Books, that stays exactly where it is. TranZact syncs one-way, so purchase data doesn’t need to be re-entered on the accounting side, and your invoice records stay consistent across both systems.

FAQs

What’s the difference between a purchase invoice and a sales invoice?

They’re the same document viewed from two sides. The seller calls it a sales invoice or tax invoice; the buyer who receives it calls it a purchase invoice.

Is a purchase order the same as a purchase invoice?

No. A purchase order is what you send requesting goods, before the sale happens. A purchase invoice is what the supplier sends back after delivery, and it’s what creates the tax liability.

Can I claim input tax credit without a purchase invoice?

No. A valid, GST-compliant purchase invoice matched in your returns is a mandatory requirement for claiming input tax credit on that purchase.

What happens if the HSN code on a purchase invoice is wrong?

It can trigger a mismatch during GST return filing, delay your input tax credit, or flag the transaction for scrutiny. It’s worth catching before the invoice is recorded, not after.

How long should purchase invoices be retained?

Under GST law, invoices and related records must be retained for at least 72 months (6 years) from the due date of filing the annual return for that year.