The storekeeper counted 96. The bill says 100.

A Tuesday at the inward gate

Lorry from the steel supplier, PO for 100 bars at ₹420 each. The storekeeper walks the length of the load, chalk in hand, and counts 96. "Count again," the supervisor says over the phone. They count again. Still 96. The GRN goes down as 96, signed, timed 11:40 am, lorry number noted.

Friday the invoice arrives: 100 bars at ₹420, taxable ₹42,000, GST 18% ₹7,560, total ₹49,560. Neat. Professional. And wrong in exactly the way that matters, because the missing four bars are worth ₹1,680 plus ₹302 of tax. Small enough to wave through. Large enough, across fifty lots a year, to buy a machine you will never own.

Two papers agree. Both are wrong.

Here is what the clerk did that Friday, and I do not blame her because the system let her. She held the invoice against the PO. Both said 100 bars at ₹420. Match. Post. That is two-way matching working exactly as designed, and it paid ₹1,982 for steel sitting in someone else's yard.

Two-way compares two papers and both papers can agree while the material falls short. It catches the supplier who raises the rate without an amended PO. It catches the 110 billed against a 100 ordered. What it cannot see, by construction, is the lorry. Nobody told it about Tuesday.

This is why I get impatient when software demos show invoice-to-PO matching as the whole answer. It is a third of the answer. The missing third has work boots on and counts things with chalk.

The match card

When all three papers exist, the decision makes itself. I keep this card pinned in my head for every dispute:

Ninety-six is what arrived, so ninety-six is what you pay. The four becomes a short-supply claim, settled by a credit note or adjusted in the next lot. No meeting about it, because the GRN was written while the steel was still warm from the lorry, not reconstructed three weeks later when everyone remembers 100.

And where does my gate sit in this picture? On the invoice card only. Checksum, fields, HSN, arithmetic within ₹1, regime. It has never met your storekeeper and it never will. What it gives you is narrower and still worth having: a bill whose totals close and whose GSTIN is real, so your clerk argues about quantities, which is the argument that saves money, instead of arguing about typos. Anyone selling an OCR row as a matched voucher is skipping the part where money leaves.

The Tuesday two-way saved

A month later, same supplier, different trick. The invoice arrives: 100 bars, all received this time, but at ₹435, not the PO's ₹420. No amended PO, no phone call, just a quiet ₹15 planted in the rate column. Taxable ₹43,500 instead of ₹42,000. The clerk, GRN habit now installed, holds three papers. GRN says 100. PO says ₹420. Bill says ₹435. Two legs agree, one leg defects, and this time the defect is the rate.

She flags it instead of posting it. Purchase calls. The supplier admits a quote-unquote system rate update and offers a choice: amended PO or credit note for the ₹1,500 difference plus tax. They take the credit note. That is two-way matching earning its keep, and notice what made it possible: the clerk had all three papers, so she knew exactly which leg was lying. Quantity was settled by the GRN in seconds, leaving the rate exposed with nowhere to hide. Most rate hikes I hear about survive because the desk is too busy arguing quantities to ever reach the rate column.

Rules of the yard

If I could pin one notice on every inward gate I visit, it would read like this. No GRN number, no voucher posting. Everything below is commentary on that sentence.

The storekeeper writes the count the day material arrives, with the lorry number on it. Morning counts beat evening memory every single time. Number every GRN off the PO plus date, because loose slips with no numbers are how 96 becomes 100 in everyone's head.

File the trio together: PO, GRN, invoice, one voucher file, physical or scanned. When the supplier disputes your short payment, you send one file, not three searches. Our vendor mapping post covers the naming discipline that makes those files findable in a hurry.

Rate differences go back to purchase, never to AP. The clerk flags; purchase negotiates or amends the PO. And tolerances, weighment loss, cutting wastage, pack sizes, get written per item by purchase, not decided per dispute by whoever shouts loudest.