Purchase Order vs Proforma Invoice

Indian manufacturing worker cutting steel stock on the shop floor, representing a purchase order becoming real production material

TL;DR: A purchase order is issued by the buyer as a binding instruction to supply goods at agreed price, quantity and terms. A proforma invoice is issued by the seller as a preliminary bill before the sale, often to confirm pricing or secure an advance payment. Confusing the two causes real problems, like treating a proforma invoice as a tax document or trying to claim input tax credit against one, both of which fail under GST.

This guide covers what separates a purchase order from a proforma invoice, when a manufacturer should expect to see each, and why only one of them can actually be used to claim GST input tax credit.

What Is a Purchase Order and What Is a Proforma Invoice?

A purchase order (PO) is a document the buyer issues to a vendor, confirming intent to buy a specific quantity of goods or services at an agreed price and delivery date. Once the vendor accepts it, it functions as a binding commercial commitment.

A proforma invoice is a preliminary bill the seller issues to the buyer before the actual sale, showing expected price, quantity and terms. It is not a legal invoice and does not create a GST liability or entitle the buyer to input tax credit.

The two documents sit on opposite sides of the same transaction and are issued by different parties for different reasons, which is why they get confused when someone assumes any document with prices and quantities on it is interchangeable.

Key Differences at a Glance

Purchase Order vs Proforma Invoice: Side by Side

The two documents differ on four points that actually matter for a manufacturer’s paperwork:

Who issues it. Buyer issues a purchase order to the vendor; seller issues a proforma invoice to the buyer, before any order is confirmed.
When it’s used. A PO confirms an order the buyer has already decided to place; a proforma invoice is often sent before that decision, to quote price and terms or support an advance payment or import documentation.
Legal weight. A PO is a binding commercial commitment once accepted; a proforma invoice is explicitly not a legal invoice and creates no obligation to pay.
GST treatment. Neither document is a GST tax invoice, but a proforma invoice specifically cannot be used to claim input tax credit, since no supply has legally occurred yet.

Diagram of the purchase management cycle: indent, RFQ, purchase order, GRN, inward QC and payment

When Each One Gets Used in Practice

The choice usually comes down to where the transaction sits in the buying cycle:

Sending a proforma invoice for approval. A vendor quotes price and terms via proforma invoice before the buyer commits, often for a new SKU or a large one-off order.
Raising a PO after accepting the quote. Once the buyer accepts the proforma invoice’s terms, they issue a purchase order to lock in the confirmed order.
Using a proforma invoice for an advance payment. Buyers sometimes need a proforma invoice to release an advance payment before the vendor starts production, especially for custom or imported goods.
Mistaking a proforma invoice for a tax invoice. The most common error is booking a proforma invoice into accounts as if it were a GST invoice, which then breaks input tax credit claims at reconciliation.
Never issuing a formal PO at all. Some SMEs skip the PO entirely and work off the proforma invoice or a verbal confirmation, which is exactly what causes duplicate or disputed orders later.

Do your vendor orders start with a real purchase order, or does a WhatsApp confirmation count as one?

TranZact turns every accepted quote into a real purchase order, tied to your actual RFQ and vendor record, so there is one document trail from quote to payment, not a proforma invoice doing double duty as a PO.

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Purchase Order vs Vendor Quotation

Stage: a vendor quotation is the earliest step, an unconfirmed price estimate; a proforma invoice is a more formal pre-sale bill; a PO is the buyer’s binding confirmation.
Issued by: quotations and proforma invoices both come from the vendor; a PO comes from the buyer.
Binding: a quotation and proforma invoice are not binding on either party; an accepted PO is a binding commitment from the buyer.
Format: quotations are often informal or verbal; a PO follows a structured format with quantity, price and delivery terms locked.
Manufacturer relevance: a factory should never release material or start production off a quotation or proforma invoice alone; only a confirmed PO should trigger action.

How TranZact Helps With Purchase Orders

TranZact turns every accepted quote into a confirmed purchase order, tied to your actual RFQ and vendor record, so every PO traces back to a real, approved requirement, not a verbal confirmation or an unconfirmed quote.

It does not replace your vendor negotiation process or decide when to convert a quote into an order. What it fixes is making sure that decision, once made, always produces a real PO other systems can trust.

FAQs

What is the difference between a purchase order and a proforma invoice?

A purchase order is issued by the buyer as a binding instruction to supply goods at agreed terms. A proforma invoice is issued by the seller as a preliminary, non-binding bill before the sale is finalized.

Can a proforma invoice be used to claim GST input tax credit?

No. A proforma invoice is not a legal GST tax invoice, so it cannot be used to claim input tax credit. Only a properly issued tax invoice, after the supply has actually occurred, qualifies.

Does a proforma invoice come before or after a purchase order?

Usually before. A seller typically sends a proforma invoice to quote price and terms, and once the buyer accepts, the buyer issues a purchase order to formally confirm the order.

Is a purchase order legally binding?

Yes, once the vendor accepts it. An accepted purchase order is a binding commercial commitment on both sides, unlike a proforma invoice or an informal quotation.

Why do manufacturers need both documents?

A proforma invoice lets a buyer confirm pricing, terms, or release an advance payment before committing. A purchase order then formalizes that commitment into a document that governs the actual order, delivery and payment.