Purchase Order (PO): What It Is & When Bookkeepers See It

Your client signs a $47,200 purchase order for inventory in March. The vendor ships in May. The invoice lands in your inbox on May 12th.

When does it hit the books?

Not March. Not "when the PO was signed." The expense hits in May, when the vendor delivers and you receive the bill. The PO itself is a commitment, not a transaction. It tells you something is coming. It doesn't create a payable until the goods arrive and the invoice follows.

That distinction sounds simple. It trips up books more than you'd expect.

What is a purchase order?

A purchase order (PO) is a buyer-issued document authorizing a vendor to supply goods or services at a specific price, quantity, and delivery date. It's a legal commitment from the buyer, but it doesn't hit the general ledger as an expense or payable when signed. It becomes a bill when the vendor fulfills the order and issues an invoice. In accrual accounting, the expense is recognized when goods are received or services are performed, not when the PO is issued. Properly managed POs flow through a 3-way match: PO, receiving report, and vendor invoice must align before the AP team pays.

Key Takeaways

• A PO is a commitment, not an expense. It creates no journal entry in most small-to-mid-size GL setups until matched to an invoice.
• The expense date is the invoice date, not the PO date. Booking at PO date is an accrual timing error that overstates prior-period costs.
• 3-way match requires three documents. PO, receiving confirmation, and vendor invoice must align on quantity and price before payment.
• PO vs. sales order: different perspectives. A PO is buyer-issued; a sales order (SO) is seller-issued. Same transaction, opposite sides.
• Open PO balances need cleanup. A partial shipment with no follow-up leaves dangling committed costs that distort AP aging reports.
• QBO Plus and Xero both support POs natively. Standalone GL users can track via memo line or a simple commitment log.

A purchase order sits in the accounting glossary right next to accounts payable and vendor credit — three related concepts that share the same vendor-bill workflow but trigger journal entries at different points.

What a Purchase Order Actually Is

A purchase order is a document your client (the buyer) sends to a vendor. It says: "We agree to buy X units of Y at $Z per unit, delivered by [date], on these payment terms."

Once the vendor accepts, both sides are bound by the PO. The buyer commits to pay. The vendor commits to deliver.

That's the legal picture. The accounting picture is different.

On the books, the PO by itself does nothing. It's not a payable. It's not an expense. You won't see a journal entry when a PO is issued. You'll see one when the vendor delivers and submits an invoice.

This is not universal. Large companies and government contractors do book POs as "encumbrances" or "commitments" in their fund accounting or ERP systems. But most small-to-mid-size businesses running QBO, Xero, or Growthy don't use encumbrance accounting. For them, the PO is a reference document, not a transaction.

Who uses POs?

POs are common in industries where purchases are planned, budgeted, and tracked:

• Manufacturing and distribution (materials, components)
• Construction (subcontractors, materials)
• Retail (inventory replenishment)
• Government contractors (required by most agencies)

Service-based businesses, including many of your SMB clients, often skip POs entirely. A law firm doesn't usually PO its office supplies. But a restaurant chain restocking from a food distributor? POs matter a lot there.

The bigger the purchase, the more POs matter. A $47,200 inventory order needs a paper trail. A $47 office supply order doesn't.

PO vs. Bill vs. Invoice: When Each Hits the Books

These three terms get conflated constantly, including by clients who should know better.

Purchase Order (PO):

• Issued by: The buyer
• Timing: Before goods/services are received
• Books entry: None (in most small-to-mid setups)
• Purpose: Authorizes the purchase, locks in price and quantity

Receiving Report (or Delivery Confirmation):

• Issued by: The buyer's receiving team (or the buyer themselves for small businesses)
• Timing: When goods physically arrive
• Books entry: None by itself, but triggers the 3-way match check
• Purpose: Confirms what actually showed up vs. what was ordered

Vendor Invoice:

• Issued by: The vendor
• Timing: After goods are shipped or services performed
• Books entry: This creates the bill in your AP
• Purpose: The demand for payment; this is when the liability is recorded

Sales Order (SO): Worth a quick note. A sales order is the vendor's internal confirmation of your PO. Your client issues a PO; the vendor acknowledges it with an SO. They're the same transaction viewed from opposite ends. A bookkeeper managing the vendor's books would see the SO. A bookkeeper managing the buyer's books sees the PO.

The 3-Way Match

Before processing payment, AP teams in larger organizations match three things:

1. The PO (what we said we'd buy, at what price)
2. The receiving report (what actually arrived)
3. The vendor invoice (what the vendor is charging)

If all three align, the bill gets approved for payment. If the invoice is for 100 units but only 80 arrived, the bill goes back to the vendor for a credit memo or revised invoice.

Many small businesses skip the formal 3-way match because they don't have a receiving department. The business owner or office manager signs for delivery and hands the invoice to the bookkeeper. That's fine for low-volume purchasing. It becomes a problem when quantities or prices drift and nobody catches it.

Common Mistakes Bookkeepers Make with POs

1. Booking the expense at PO date instead of invoice date

This is the most common timing error. A client sends a $47,200 PO in March. The goods don't arrive until May. The invoice is dated May 12th.

If you're working in accrual accounting, March is wrong. The expense belongs in May, when the vendor fulfilled the order and the liability arose.

Why does it happen? Sometimes the client's team enters the PO directly into their bill system as if it were a bill. Sometimes a bookkeeper assumes "signed means booked." Neither is correct.

The impact: March expenses are overstated. May expenses are understated. The P&L misrepresents both months. For a business owner making decisions on monthly financials, this matters.

2. Leaving open PO balances unclosed after partial shipments

A client orders 500 units. The vendor ships 300 in April and 200 in June. The April invoice covers 300 units. The June invoice hasn't arrived yet.

The June portion of the PO is still "open." If nobody tracks it, it disappears from sight until the June invoice shows up. No problem if the vendor invoices promptly. Big problem if the vendor never invoices the remainder, or if the client assumes the order is complete when it isn't.

Open PO balances that never close create two issues: (1) the AP team may double-pay if they can't match the second invoice to the original PO, and (2) the committed cash outflow is invisible to whoever is doing cash flow planning.

3. PO number mismatches breaking the 3-way match

The PO says PO-2026-0847. The vendor's invoice references PO-847. The receiving team's log just says "April order." Three references to the same transaction, none of them matching exactly.

For a small business with 10 POs a year, someone manually connects the dots. For a business with 200+ POs, mismatched references mean invoices sit in limbo, AP aging ages incorrectly, and vendors start calling.

The fix is upstream: enforce a consistent PO numbering format and require vendors to include the exact PO number on all invoices. That's a process conversation with the client's ops team, not just a bookkeeping fix.

4. Confusing PO with sales order

A client sends you a "purchase order from a customer." That's not a PO from the buyer's perspective. That's a sales order from the seller's perspective. The client is the seller in this transaction.

The terminology matters because it determines which set of books you're updating. A sales order from a customer goes into the client's AR workflow, not AP. Mixing them up creates entries on the wrong side of the ledger.

How Growthy Handles PO Workflows

PO management is mostly a tracking and matching problem, not a categorization problem. By the time a vendor invoice hits the bank feed or the bill queue, the PO has already done its job.

For clients running QBO Plus or QBO Advanced, PO tracking is built in. QBO creates the PO, tracks it against the bill when the invoice arrives, and marks the PO closed when matched. If your client is on QBO Plus or higher, the PO workflow runs inside QBO and you're reviewing the matched results.

For clients on Growthy's standalone GL, the workflow is lighter. Since most SMB clients don't have formal purchasing departments, POs often show up as reference numbers in the bill description or memo line. Growthy's transaction review surfaces the vendor invoice in the normal AP queue. A simple commitment log (even a spreadsheet) tracks open POs and their expected invoice dates. When the invoice arrives, you match it to the log, confirm quantities, and post the bill.

Where Growthy adds value is in the downstream reconciliation. When the same vendor sends monthly invoices with varying amounts, pattern learning catches inconsistencies. A $12,000 invoice from a vendor whose last six invoices averaged $4,200 flags for review. That's not a PO mismatch, but it's the kind of signal that surfaces the "we got overcharged on the second shipment" problem before you pay it.

If you're reconciling AP aging and notice open PO balances from three months ago, that's the signal to dig. Either the second shipment never arrived, the invoice is sitting in someone's email, or the vendor never completed the order.

FAQ

Is a purchase order the same as a bill?

No. A purchase order is a commitment to buy. A bill (or vendor invoice) is the demand for payment after the vendor fulfills the order. The PO comes first. The bill comes when goods are delivered or services are performed. In accrual accounting, the bill is when the liability hits the books, not the PO.

When does a purchase order become an expense?

When the vendor delivers the goods or completes the service and sends an invoice. That invoice date determines when the expense is recorded in accrual accounting. If the PO is signed in March and the invoice is dated May 12th, the expense belongs in May.

What is the 3-way match in accounts payable?

The 3-way match is a check performed before paying a vendor invoice. It compares three documents: (1) the original purchase order, (2) a receiving report confirming what arrived, and (3) the vendor invoice showing what's being charged. All three must agree on quantity and price before the bill is approved for payment. If they don't match, the invoice is put on hold until the discrepancy is resolved.

What's the difference between a purchase order and a sales order?

A purchase order (PO) is issued by the buyer. A sales order (SO) is issued by the seller in response to a PO. They reference the same transaction from opposite sides. If your client is the buyer, they issue POs. If your client is the seller, they receive POs from customers and create SOs internally. The bookkeeping entries are different in each case.

Does every business need to use purchase orders?

No. Many service-based SMBs don't use POs at all. They buy when they need to and pay when the invoice arrives. POs become important when purchases are planned in advance, involve significant amounts, or require formal approval before spending. Construction, manufacturing, distribution, and government contractors rely heavily on POs. A solo consultant or small law firm probably doesn't need them.

Does QBO support purchase orders?

Yes, but only on QBO Plus and higher (not Simple Start or Essentials). Xero also supports purchase orders on all plans. Dedicated procurement tools (Precoro, Procurify, and similar) handle more complex workflows at higher price points, including multi-step approval routing and ERP integration. For most small business clients, QBO Plus is enough.

Most of your clients won't think much about purchase orders. But when a $47,200 inventory PO shows up in March and the client expects to see the expense that same month, you'll need to explain why it belongs in May. That conversation goes smoother when you understand the mechanics cold.

The books should reflect economic reality. The PO is a promise. The delivery is the event. The invoice is the trigger.

Ready to close faster and catch these before they land in your AP queue? Start with Growthy free.