Automating procure-to-pay: requisition to PO to GRN to 3-way match

Purchase is where a lot of money leaves a manufacturing or contracting business, and where a surprising amount of it leaks. Material is ordered twice because two people raised the same request. A supplier invoice is paid at a higher rate than the purchase order. Goods are paid for that never arrived, or arrived short. None of this needs fraud; it only needs a process that relies on phone calls and memory.

Procure-to-pay (P2P) is the name for the whole chain, from someone needing material to the supplier being paid. This article walks through each step, what to control at each one and where automation genuinely helps.

The chain at a glance

Step	Document	Key control
1. Need identified	Requisition or material request	Is this genuinely needed, and not already in stock?
2. Approval	Approved requisition	Has the right person agreed?
3. Order	Purchase order (PO)	Right supplier, right rate, right terms
4. Receipt	Goods receipt note (GRN)	What actually arrived, in what quantity
5. Invoice	Supplier invoice	Does it agree with the PO and the GRN?
6. Payment	Payment entry	Pay only what is matched and due

Each step produces a record that the next step depends on. Skipping one does not save time; it just moves the problem downstream.

Step 1: the requisition

A requisition says “we need this”. In a panel shop it often comes from a sales order that is short of material. On a construction site it comes from the site engineer as a material request.

Good requisitions are:

• Tied to a reason, such as a job, a sales order or a project.
• Checked against stock, so you do not buy what is already in the store. On a construction project, a material request can be split into what can be issued from stock and what must be purchased.
• Specific, with item codes rather than free-text descriptions where possible.

Automation that helps

The biggest gain here is generating requisitions from shortages automatically. When a sales order or job needs material that is not in stock, the system should list the shortfall and raise the requisition, rather than waiting for someone to notice.

Step 2: approval

Approval is where you decide whether the spend is justified. Two practical approaches work well:

• Approval by role, where requisitions above a certain level need a manager’s sign-off.
• Approval by value, where purchase orders above a threshold need a higher authority. This keeps routine small orders moving while large commitments get scrutiny.

The approver should see why the material is needed and what it is for. An approval screen that shows only an amount invites rubber-stamping.

Step 3: the purchase order

The PO is your commitment to the supplier. Controls that matter:

• Supplier and rate chosen deliberately. Comparing current price lists from several vendors before ordering is one of the simplest ways to save money.
• Grouping by vendor. Approved requisition lines for the same supplier should become one PO, not ten.
• A duplicate-order check. Two POs for the same material on the same job is a common and avoidable mistake.
• A clear status, from draft through approved and sent to received.

Automation that helps

An agent can look at approved requisitions or shortages, pick the cheapest vendor from your price lists and prepare draft POs grouped by supplier. A purchase manager reviews and approves them. This is far quicker than building each PO by hand, and the decision stays with the person accountable for it.

Step 4: goods receipt

The GRN records what physically arrived. It should be the only way stock enters your books. If material can appear in stock any other way, your stock figures and your cost figures will drift apart.

At receipt, check:

• Quantity received against quantity ordered.
• Item and specification against the PO.
• Damage or rejection, recorded at the time.

Automation that helps

Suppliers send invoices and delivery challans as PDFs and photos. AI can read these documents, match them to the open PO and prepare a draft GRN with any differences flagged. The store keeper confirms what was actually received. Nothing should be posted until that confirmation.

Step 5: 3-way match

Before an invoice is paid, three documents should agree:

1. The purchase order: what you agreed to buy, and at what rate.
2. The GRN: what you actually received.
3. The supplier invoice: what the supplier is asking you to pay.

If the invoice quantity exceeds the received quantity, or the invoice rate exceeds the PO rate, the difference should be held until resolved. This one control catches over-billing, short supply and rate creep.

Remember GST on the invoice as well: the supplier’s GSTIN, HSN codes and tax split should be correct, because your input tax credit depends on them.

Step 6: payment

Pay what is matched and due under the agreed terms. A payment register that links each payment to the supplier invoice it settles keeps your payables position accurate and makes supplier reconciliation straightforward.

Getting the basics right first

Automation amplifies whatever process you already have. Before automating, make sure:

• Your item master is clean, without duplicates.
• Your vendor master has correct GSTINs and contacts.
• Price lists from your main suppliers are current.
• Everyone agrees that stock enters only through a GRN.

Where Zaptiz fits

Zaptiz Electrical runs the full chain. Requisitions can be raised from sales-order shortages, with a supplier set per line, approved and converted into POs grouped by vendor. POs move from draft to approved, sent and received, with print, email and WhatsApp. Confirming a GRN is the single, auditable way stock enters. Supplier invoices go through a 3-way match across PO, GRN and invoice before payment, and vendor price comparison ranks vendor price lists cheapest first. The Smart Procurement agent drafts purchases from the cheapest vendor, and the Invoice and Delivery Reader reads supplier documents, matches the PO and drafts the GRN. Vendor comparison works from price lists; recording RFQ responses from suppliers is not supported today.

Zaptiz Construction covers material requests split into from-stock and to-purchase, POs with an approval tier set by order value and a duplicate-order guard, and GRNs that update stock and move committed cost into inventory. Its Procurement Agent turns approved-but-unordered material into draft POs per vendor, and the Invoice and Challan Reader drafts GRNs with differences flagged. Supplier invoice 3-way matching and vendor price comparison are Electrical features today.

For the Electrical walkthrough, read Purchase to stock in Zaptiz Electrical, or compare both products on the features page.