Overview
Paying an invoice without verifying it matches an approved purchase order is one of the most common causes of accidental overpayment and vendor fraud in small businesses. Bill.com's purchase order matching feature flags invoices that don't match an existing PO — wrong amount, wrong vendor, or no PO at all — before they reach the approval queue. This creates a systematic check that catches errors before money leaves the account.
Before you start
- Bill.com Team plan or higher (PO feature)
- Existing approval workflow in Bill.com
- Zapier for Slack alerts (optional)
Step-by-step guide (4 steps)
Enable purchase orders in Bill.com
Go to Bill.com → Settings → Purchase Orders → Enable Purchase Orders. This activates the PO module in Bill.com. POs can now be created, approved, and linked to incoming invoices.
Create POs for all significant purchases
Before ordering from a vendor, create a Purchase Order in Bill.com: vendor, line items, quantities, unit prices, expected delivery date. Route the PO through your approval workflow before it's issued. The approved PO is your authorization baseline for payment.
Link incoming invoices to POs
When a vendor invoice arrives, open it in Bill.com and click 'Match to PO'. Bill.com shows open POs from that vendor. Select the matching PO. Bill.com compares line items, quantities, and amounts between the invoice and PO and flags discrepancies.
If the invoice amount differs from the PO by more than 10%, flag it for manual review before approving payment. Minor discrepancies (shipping charges) can be approved; major ones need vendor clarification.
Set up a Zapier alert for unmatched invoices
Create a Zapier workflow: when a Bill.com invoice is created without a matching PO tag, send a Slack message or email alert to the AP manager: 'Invoice #[X] from [Vendor] for $[Amount] has no matching purchase order. Review before approving.'
What you'll get
Prevents payment of invoices without authorized POs
Catches vendor overbilling by comparing invoice to PO line items
Creates a clear authorization trail for every purchase
Reduces accidental duplicate payments from processing the same invoice twice
Common mistakes to avoid
Creating POs after the fact to match invoices — defeats the purpose of the process
Not enforcing the PO requirement consistently across departments
Approving invoices with significant PO discrepancies without vendor clarification
Not using PO matching for small recurring vendors — fraud often starts small
Frequently asked questions
Do I need coding experience to set up this Bill.com automation?
No coding is required. This guide walks you through everything using Bill.com's built-in features and Zapier's visual interface. If you can follow a recipe, you can follow this guide.
How long does this automation take to set up?
Most users complete this setup in 30–60 minutes on their first try. Once set up, it runs completely automatically with zero ongoing effort.
What happens if the automation fails?
Zapier and Make both have error notifications and task history, so you'll know immediately if something goes wrong. We cover troubleshooting steps in the guide above.
Can I customize this automation for my specific business?
Absolutely. The guide includes notes on common customizations. Most automations have multiple variation points — timing, conditions, notification recipients, and more.