The Accounts Payable Process, Step by Step

Accounts payable is the money going out for goods and services you've already received but haven't paid for yet. On the balance sheet it's a liability; day to day it's a queue of bills moving through five stages: a vendor gets set up, an invoice arrives and gets entered, the invoice gets checked against what was ordered and received, someone with authority approves it, and then it gets paid on a schedule rather than the moment it lands in the inbox.

Most small businesses run this on gut feel until the bill volume outgrows one person's memory. A missed early-payment discount, a bill paid twice because it arrived by email and by mail, or a vendor who never sent a W-9 and now needs a 1099 in three weeks are all symptoms of the same thing: no defined process. The fix isn't more software. It's writing down who does each of the five steps and making sure no one person does all five alone.

For context on where AP sits inside the wider close, see our month-end close checklist; AP is one of the ledgers that has to be clean before the books close.

Before you pay a new US vendor for services, get a completed and signed Form W-9 from them. It gives you their legal name, entity type, and taxpayer ID number, and it's the only way you'll know later whether that vendor needs a 1099. Waiting until January to chase down W-9s from a dozen vendors is the single most common AP scramble, and it's entirely avoidable: make the W-9 a condition of the first payment, not a follow-up.

While you're at it, capture a few other things once, at setup, instead of chasing them per invoice: the vendor's preferred payment method (ACH, check, card), remit-to address if it differs from the mailing address, standard payment terms, and a single point of contact. Store this in your accounting software's vendor record, not in a spreadsheet that lives on one person's desktop.

A quick sanity check at onboarding: is this vendor actually an independent contractor, or should they be on payroll? Getting that wrong has payroll tax consequences well beyond AP. If you're not sure, that's a question for whoever runs your payroll, not a guess made by whoever happens to be entering the vendor.

An invoice can arrive by email, mail, a vendor portal, or handed over at a job site. Wherever it lands, it needs one thing to happen fast: it has to get into your accounting system, not sit in an inbox. Tools like Bill.com, Melio, or the bill-capture features inside QuickBooks Online and Xero can pull data off a scanned invoice automatically, but someone still has to check the amount, the vendor, the invoice number, and the general ledger account it's being coded to.

Coding is where a lot of AP quality is won or lost quietly. An invoice coded to the wrong expense account doesn't cause a payment problem, it causes a reporting problem: your management reports understate one line and overstate another, and nobody notices until the numbers look strange months later. A short, current chart of accounts with clear rules for common vendors (which utility goes where, which software subscription is which category) cuts this error rate more than any software feature does. See our chart of accounts design guide if that structure isn't solid yet.

Duplicate invoices are the other recurring issue: the same bill submitted twice, once on paper and once electronically, or resent after a vendor's system glitches. Checking the invoice number against what's already in the system before entering a new one catches most duplicates before they become duplicate payments.

Three-way match means an invoice only gets approved for payment once it lines up with two other documents: the purchase order (what you agreed to buy, at what price) and the receiving record (confirmation that you actually got the goods or the service was delivered). If the invoice quantity or price doesn't match the PO, or nothing was received against it, it gets flagged before payment, not after.

How the matching levels compare:

• No match (approval only): an approver reviews the invoice on its own judgment, no PO or receiving record involved. Fastest, weakest control. Fits small, low-dollar, one-off bills.
• Two-way match: invoice checked against the purchase order only (same vendor, price, quantity ordered). Catches pricing and quantity errors. Doesn't catch billing for something never delivered.
• Three-way match: invoice checked against both the purchase order and the receiving record. Catches everything two-way catches, plus phantom or partial deliveries. Best fit for goods and recurring high-dollar services.
• Four-way match: adds a quality-inspection sign-off on top of three-way. Used mainly in manufacturing or regulated goods, rarely needed for a typical services business.

A reasonable rule many businesses use: require a PO and three-way match above a set dollar threshold you choose, and let smaller, routine bills go through two-way match or a simpler approval below that. Three-way match is manual work if you're doing it in a spreadsheet, and it's one of the first things worth automating once bill volume passes roughly 50 to 100 invoices a month, because that's usually the point where matching by memory starts producing errors instead of catching them.

Every invoice needs one person accountable for saying yes, this is real, this is correct, pay it. That person should be someone with knowledge of the purchase, usually whoever requested the goods or service or their manager, not whoever happens to be doing data entry that day.

Set a simple approval ladder based on dollar amount: a department head can approve up to a set limit, anything above that needs a second signer, and unusual vendors (brand new, or paid for the first time in a while) get a second look regardless of amount. Bill.com and Melio both support this kind of tiered routing natively, so it doesn't have to live in someone's head or in email threads that get lost.

The control that matters most here isn't the ladder itself, it's that the approver and the payer are different people. If the same person who says "pay this" is also the one who clicks send on the payment, there's no independent check on either step, and that's exactly the gap most AP fraud walks through.

Paying bills the moment they're approved feels responsive but it's expensive in a different way: it means you're never using the full payment terms a vendor gave you, and it turns AP into a constant drip instead of a predictable weekly or biweekly task. Most businesses are better served by a scheduled payment run, once a week or twice a month, where everything approved and due gets paid in one batch.

Payment method matters for cost and speed. ACH is cheap and usually settles in one to two business days; checks are slower and carry a real cost once you count postage, stock, and the staff time to print and mail them; card payments can earn rewards but sometimes carry a vendor surcharge you need to negotiate or absorb. None of these is universally right, match the method to what the vendor accepts and what you're optimizing for.

Early payment discounts (commonly written as terms like "2/10 net 30," meaning 2 percent off if paid within 10 days instead of the full 30) are worth calculating before you dismiss them. Taking a 2 percent discount for paying 20 days early is equivalent to a strong annualized return; it's usually worth taking if you have the cash on hand.

The controls that do the most work are the boring ones, repeated consistently:

• Segregation of duties: the person entering invoices, the person approving them, and the person releasing payment are three different people (or at minimum, two, with the smallest business owner keeping final release authority)
• A documented approval limit by dollar amount, enforced by the payment tool, not by trust
• New vendor and vendor bank-detail changes get a phone call or a second verification, never approved off an email request alone (business email compromise scams specifically target vendor payment-detail changes)
• Duplicate invoice numbers are blocked at entry, not caught after payment
• Someone outside the AP process reviews the vendor list and payment register periodically, looking for vendors that don't map to a real business relationship

None of this requires expensive software. It requires deciding, in writing, who does what, and then not making exceptions for convenience. The exceptions are where the losses happen.

The IRS reporting threshold for Form 1099-NEC nonemployee compensation payments rises from $600 to $2,000 for payments made in 2026 and later years. That's a real change worth knowing, because it means fewer small vendors will cross the threshold going forward, but it doesn't remove the need to track who you're paying and how much.

The practical habit: whenever a new vendor is onboarded, note their entity type from the W-9 (corporations are generally excluded from 1099-NEC, most individuals, partnerships, and LLCs taxed as such are not) and flag them for 1099 tracking if they're a service provider paid in cash, check, or ACH. Payments made through a third-party payment network or by credit card are typically reported by the payment processor instead, on a 1099-K, so they shouldn't be double-counted on your 1099-NEC.

Form 1099-NEC must be filed with the IRS and furnished to recipients by January 31, whether filed on paper or electronically, so this isn't a task that fits into a slow January. Running a vendor payment total report in December, before the year closes, gives you time to chase a missing W-9 or a wrong taxpayer ID while there's still room to fix it. For the full mechanics see our Form 1099 guide.

At month end, AP needs to answer one question cleanly: what do we owe, as of the close date, that hasn't been paid yet? That means recording an accrual for goods or services received but not yet invoiced (a delivery that came in on the 29th with the invoice not arriving until the following month), and making sure every invoice dated in the period is actually recorded in that period, not the next one because it was still sitting in someone's inbox.

A short AP aging report, sorted by how overdue each bill is, should be part of every month-end review. It surfaces two different problems at once: bills that are overdue because of a cash crunch, and bills that are overdue because they were simply never processed. Those need very different fixes.

Reconcile the AP subledger total against the accounts payable balance on the balance sheet before you call the close done. A mismatch there almost always means an invoice was entered twice, entered to the wrong account, or paid outside the normal AP workflow (a card payment or a wire that bypassed the bill-entry step) and never cleared out of the ledger.

Days payable outstanding (DPO) is the headline number: it estimates how many days, on average, it takes you to pay your bills. The formula is accounts payable balance divided by cost of goods sold (or total purchases), multiplied by the number of days in the period.

Worked example: say your AP balance at month end is $84,000, and your cost of goods sold plus operating purchases for that 30-day month totaled $252,000. DPO equals $84,000 divided by $252,000, times 30 days, which comes out to 10 days. That means, on average, you're carrying about 10 days of purchases as unpaid bills at any point. If next month your AP balance rises to $126,000 on the same $252,000 of purchases, DPO jumps to 15 days. That could mean you're deliberately using more of your payment terms and holding cash longer, a reasonable cash-management move, or it could mean bills are simply going unpaid past their due dates. The number alone can't tell you which; check it against your AP aging report and your cash balance before drawing a conclusion.

A rising DPO can mean you're managing cash well by stretching payment terms, or it can mean you're falling behind, so read it alongside your cash balance, not alone.

A few supporting metrics worth tracking monthly:

• Invoice processing time: days from invoice received to invoice approved. Long lag times here usually point to a bottleneck in approval, not in data entry.
• Percentage of invoices matched on the first pass, without a manual correction. A falling percentage is an early sign that vendor pricing or PO discipline is slipping.
• Early payment discounts captured versus discounts available. This one has a direct dollar value and is easy to leave on the table without noticing.
• Number of vendor payment disputes per month. Rising disputes often trace back to a coding or matching error upstream, not a vendor problem.

None of these need a dashboard to start. A simple monthly count in a spreadsheet, reviewed for trend rather than a single month's number, catches most of what matters.

A few patterns show up again and again in businesses that haven't formalized AP yet:

• One person does everything (entry, approval, and payment), usually the owner or office manager, which works until volume grows or that person is out sick during a payment run
• New vendors get paid before a W-9 is collected, and by the time 1099 season arrives, several vendors are unreachable or the taxpayer ID on file is wrong
• Invoices sit in an email inbox instead of the accounting system, so nobody has a single view of what's actually owed
• Payment terms are accepted from vendors without checking them against cash flow, so bills come due faster than collections come in
• Vendor bank-detail changes are actioned from an email request alone, which is exactly the scenario business email compromise fraud is built around

Each of these is fixable with a written process and a second set of eyes, not with a bigger software budget. Software helps enforce a process that's already been decided; it doesn't create the process for you.

A lot of businesses run AP internally just fine at low volume with one disciplined person handling it. The signals it's time for outside support: invoice volume has outgrown one person's available hours, the person handling AP is also the only check on it (no segregation of duties possible with current headcount), 1099 tracking is a January fire drill every year, or you simply want a second set of eyes on vendor payments without hiring a full-time controller.

Outside AP support typically covers invoice entry and coding, three-way match, payment-run preparation (queued for your approval, never released without it), vendor W-9 collection, and 1099 tracking through the year rather than in a scramble. It doesn't typically include taking custody of your bank credentials or releasing payments without your sign-off; a properly run engagement keeps that authority with you unless you explicitly delegate it in writing.

If AP is one piece of a broader bookkeeping gap, it's usually worth fixing alongside the rest of the ledger rather than in isolation; see our bookkeeping basics guide for how AP fits into the full monthly close.