The Supplier Invoice No One Can Approve

A supplier invoice lands in your inbox. It is for materials you know were ordered, from a supplier your team has worked with before. The amount looks roughly right. But nobody can confirm the price that was agreed, the quantity that was expected, or who actually authorized the order. The invoice sits in a queue while someone tries to piece together what happened - and your supplier, who is waiting on payment, starts to get impatient.

This scenario plays out across small and medium-sized businesses every week. Not because teams are disorganized, but because most day-to-day ordering does not start with a formal purchase order. It starts with an email, a text message, a phone call, or a verbal agreement on a job site. By the time the invoice arrives, the original commitment is buried in someone's inbox - or missing entirely.

The Informal Order Is the Root Cause

Small and medium-sized businesses place orders quickly, often under pressure. A site manager needs materials delivered tomorrow. A production coordinator calls a supplier to confirm availability and adds extra units to an existing delivery. A business owner approves a purchase verbally during a client call. In each case, the order goes out but the formal record never follows.

The problem does not surface at the point of ordering. It surfaces when the invoice arrives. By that point, the original conversation is days or weeks old. The person who placed the order may not remember the exact price they were quoted, the quantity they confirmed, or whether they even authorized a particular line item. Finance has no way to verify any of it.

What Three-Way Matching Requires

The standard approach to invoice approval in businesses with defined processes is three-way matching: comparing the supplier invoice against the original purchase order and the goods received note to confirm that what was ordered, what was delivered, and what is being charged all line up.

Three-way matching catches price discrepancies before payment goes out. It flags invoices for quantities that were never received. It creates a documented audit trail for every transaction. But it cannot function without a purchase order to match against. When the original commitment was made verbally or by email, the first leg of the match is simply missing.

Research published in April 2026 found that 76% of organizations reported attempted or actual payment fraud in 2025. Invoice fraud most commonly targets businesses that do not systematically match invoices to purchase orders, because there is no documented baseline to measure the invoice against. A fraudulent invoice from a known supplier name, in a plausible amount, can pass informal approval processes simply because nobody has grounds to question it.

The Downstream Consequences of Ordering Without POs

When orders go out without purchase orders, the effects accumulate across procurement, finance, and operations.

Duplicate orders. Without a central record of what has been ordered, the same item gets ordered twice - once by the person who handles procurement and once by the person who needed it urgently. Both suppliers deliver. Both invoice. Both expect payment.

Price disputes. A supplier quotes £420 per unit on the phone. By the time the invoice arrives at £455, the person who took the original call has moved on to other jobs. Finance has nothing to dispute against because there is no document recording what was agreed.

Strained supplier relationships. A payment that should take 30 days takes 60 because accounts payable is waiting for someone to authorize an invoice that has no supporting documentation. Suppliers notice. Some respond by tightening payment terms or deprioritizing orders from businesses that pay slowly and dispute frequently.

Job costing gaps. When purchase orders are not raised against specific jobs, there is no way to track what was spent on each project. Invoices get coded to general overheads, and the cost of each job stays invisible until someone manually reconciles it at month end - if it gets reconciled at all.

What a Purchase Order Actually Does

A purchase order is not a bureaucratic extra step. It is the document that makes every subsequent step in the procurement process work. It records what was agreed before the order goes out, which means every subsequent check - delivery, invoicing, payment - has a baseline to compare against. Without it, those checks happen in reverse, working backward from an invoice to reconstruct a commitment that should have been documented at the start.

For businesses managing multiple active jobs, purchase orders also carry the information needed to allocate costs correctly at the project level. A PO tied to a specific job number means the invoice that follows can be matched to that job automatically. The alternative is someone manually cross-referencing invoices against job records at month end, which takes time that most small businesses do not have.

Zigaflow's purchase orders feature ties each PO to the quote or job it supports, so the chain from customer order to supplier commitment to delivery to invoice is traceable in one system. When a supplier invoice arrives, the matching documents are already there. Approval becomes a verification step rather than a guessing exercise, and the job cost updates automatically rather than waiting for a manual reconciliation.

For a checklist of what every purchase order should contain before it goes to a supplier, see Five Things Every Purchase Order Should Include.

What to Change First

The invoice that nobody can approve is not a finance problem. It is a procurement process problem, and it starts at the moment an order goes out without a formal record behind it. Fixing it means making the purchase order the starting point for every supplier commitment - not the document that gets created after the fact to tidy up an invoice that has already arrived.

That shift is less about enforcing discipline and more about having a process that makes raising a PO no harder than sending an email. When the two take the same amount of effort, the informal workarounds disappear on their own.

Sources

• 3-Way Matching in Accounts Payable: How It Works and Why It MattersPrecoro · accessed 2026-08-06
• Invoice Discrepancies: Types, Causes & How to Resolve ThemRamp · accessed 2026-08-06

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