Three-way matching: How to incorporate it into your accounts payable process

Early-stage companies often have fast-moving processes. Vendors are onboarded quickly, invoices arrive via email and Slack, and payments may be approved between customer calls and product launches.

This speed is often necessary, but it requires structure and safeguards to avoid errors, like duplicate invoices getting paid by two different people, subscription renewals slipping through unnoticed, or a team member placing an order without formal approval. None of these mistakes feel catastrophic in isolation, but over time, they chip away at cash, credibility, and operational discipline. 

Aside from human errors, organizations also lose an estimated 5% of their revenue to fraud each year. 

If you’re building your first structured accounts payable workflow, here’s what to know about three-way matching, including how it works and how to implement it without slowing your team down.

Any money that flows out of your business needs to be approved by accounts payable, typically by comparing it to other documents. For the best assurance, you can use a three-way matching approval process to verify a bill should actually be paid. A three-way match holds the line — not as a bureaucratic hurdle, but as a lightweight control to protect your business while your startup scales.

Specifically, an accounts payable three-way match compares three documents:

1. The purchase order (PO)
2. The goods receipt (or proof of service delivery)
3. The vendor invoice

When the terms, quantity, and price in these three documents align, the accounting department approves the invoice for payment. If these three elements don’t match, the discrepancy must be resolved before funds are released from your account.

Three-way matching in accounts payable ensures that you’re only paying for what you ordered and what you actually received. For early-stage teams, this level of clarity matters, since your business probably can’t afford mistakes that eat up cash. And these simple and effective controls can work well for a small team.

To understand how three-way matching works, it helps to break down what each document verifies.

1. Purchase order (PO)

Issuing a purchase order is the authorization step. For lean teams, a PO might be as simple as a formal approval in your system, rather than a multi-page document. What matters is that the purchase is intentional and authorized before spending occurs

A purchase order outlines:

• What’s being purchased
• The agreed-upon price
• Quantities
• Payment terms
• The approving party

2. Goods receipt or proof of delivery

The goods receipt or proof of delivery document confirms that a vendor delivered what you actually ordered. For physical goods, this might be a receiving report. For services, it could be confirmation that the work was completed, a milestone was reached, or a contract term was fulfilled. Without this step, you’re relying solely on a vendor’s invoice to tell you that something happened.

3. Vendor invoice

A vendor invoice is a request for payment. The invoice is what triggers the payment process, but it should never be the only document you rely on. 

The vendor invoice should reflect the same details seen in the PO:

• The same quantity
• The same pricing
• The same terms

Here’s a simplified, step-by-step version of how three-way matching works in practice:

1. A department submits a purchase request.
2. The request is approved, and a purchase order is issued.
3. The goods or services are delivered and confirmed.
4. The vendor submits an invoice.
5. Accounts payable compares the PO, receipt, and invoice.
6. If everything matches, the invoice is approved and scheduled for payment.
7. If something doesn’t match, it’s flagged for review

As you build an accounts payable process for your startup, you may wonder about this important operational question: How does three-way matching prevent costly procurement mistakes? 

The value of the three-way approach is that it prevents just one single document from triggering payment. Instead, this system of checkpoints requires alignment across authorization, delivery, and billing, which dramatically reduces errors. Adding more controls might sound like it’ll lead to slower processes, but a well-designed three-way match prevents rework and cash leakage, which can, ultimately, save time. 

Three-way matching can protect your company against the following issues.

Duplicate payments

Without a structured accounts payable process, it’s surprisingly easy to pay the same invoice twice, especially if invoices are submitted via multiple channels. By matching each invoice against a unique PO and receipt, you’ll create a checkpoint that makes duplicate invoices easier to catch.

Overbilling or pricing errors

If a vendor invoices for 120 units instead of 100 or bills for a price that differs from the PO, a three-way matching system will catch the discrepancy before payment. This can save significant money over time.

Unauthorized purchases

If you receive an invoice without a corresponding PO, that’s a signal that there could be a breakdown in your approval workflows. Instead of normalizing off-the-books purchases, encourage clear and sustainable spending habits by building easy-to-use systems for getting purchases approved in advance. .

Paying for undelivered goods or incomplete services

By matching against a goods receipt, your team can ensure that work was actually performed before funds are released for payment. This is especially critical in project-based or milestone-driven work.

Not every startup needs a heavyweight system on day one. Understanding the differences between two-way and three-way matching will help you make an intentional choice that matches your company’s needs.

Before building a process, assess your startup’s transaction volume, vendor complexity, and risk tolerance. Then, determine which approval system is right for you.

For early teams with minimal spend, a two-way match may feel sufficient. But as soon as you scale vendor relationships or increase purchasing complexity, a three-way match will provide meaningful additional protection.

You don’t need an enterprise-level accounts payable department to implement a three-way match system well, but you do need a clear view of your workflow and potential gaps. 

Here are three-way match best practices that work for early-stage companies.

1. Create simple PO policies

Define when a purchase order is required, and keep your rules clear and easy to follow.

For example, you could require a PO for:

• All purchases above a certain dollar threshold
• All new vendors
• All recurring contracts

2. Set approval thresholds

Not every purchase requires founder approval. Define spending tiers so routine expenses move quickly and larger commitments receive more oversight.

3. Standardize documentation

Require vendors to include PO numbers on their invoices, and consistently document any goods receipts or service confirmations. These small, beneficial operational habits compound over time.

The biggest mistake that startups make when setting up three-way matching is overengineering the system, which creates friction. If your approach involves too much administrative drag, your team will likely abandon it when things get busy. For instance, ff approvals require five signatures and three email threads, team members may route around the system to save time.  To build a workflow that fosters disciplined speed and financial clarity, design a system that’s easy for your team to adopt.

To avoid bottlenecks, try these tips:

• Automate routing where possible.
• Keep approval chains short.
• Use software to flag mismatches automatically, rather than relying on manual spreadsheet comparisons.

Manual matching works at low volume, but most finance teams can confirm that it breaks at scale. This is where automation and modern financial infrastructure shines. 

To help you streamline your processes, Mercury brings multiple financial workflows into a single product experience. Instead of juggling separate systems for approvals, payments, and cash visibility, teams can build lightweight controls directly into the places where your money moves.

Automation tools can:

• Link POs to invoices automatically.
• Flag mismatches instantly.
• Prevent payments from being scheduled without proper documentation.
• Create a clear audit trail.

A structured approach to accounts payable three-way match becomes much easier when payment tools and approvals live in the same ecosystem. You’ll reduce manual work while strengthening controls, which is exactly the balance early-stage teams need.

By rolling out a smooth-running three-way match process, you’ll bring added clarity and consistency to your operations.. This discipline can build trust with vendors, confidence with investors, and operational maturity within your team.

Using a three-way match creates a reliable system where:

• Purchases are intentional.
• Deliveries get confirmed.
• Payments are accurate.

Implementing three-way matching in accounts payable early, even in a lightweight form, lays the groundwork for scalable, resilient operations. With modern platforms, like Mercury, supporting you with bill pay and approval workflows, you can introduce meaningful controls without sacrificing speed. When your financial infrastructure grows with you, you’ll spend less time fixing mistakes and more time building what actually matters.