Quick Answer
Run seven checks before you pay an invoice: did you order it, is the sender genuinely who they say, is the document actually an invoice rather than a quote or a solicitation, does the arithmetic hold, is it billed to your legal entity, have you already paid it, and when is it really due. Most bills clear all seven in under a minute; the failures are where duplicate payments and fraud live. Treat any change of bank details as unverified until you confirm it by voice on a number you already had, because details that arrive by email are the most expensive failure on the list. Get a contractor's W-9 before you pay rather than the following January, keep the invoice and the proof of payment together, and always reply to a payment reminder with a specific date rather than an apology.
An invoice that lands in your inbox is a request, not an instruction. Before any money moves, run seven checks: did you order it, is the sender really who they say, is it actually an invoice, do the numbers add up, is it billed to the right entity, have you already paid it, and when is it genuinely due. Most bills clear all seven in under a minute. The ones that do not are where duplicate payments, overcharges and outright fraud live. This guide covers the check itself, how to tell a fake invoice from a real one, the tax paperwork you need before you pay a contractor, what to write back in each case, and what to keep afterwards.
The Seven-Point Check Before You Pay
Large companies run this through an approval workflow with three sets of initials on it. A one-person business runs it in the sixty seconds between opening the PDF and opening the banking app. The checks are the same either way, and the order matters — the cheap ones that catch the expensive mistakes come first.
| # | Check | What you are looking for | If it fails |
|---|---|---|---|
| 1 | Did you order this? | A quote you accepted, a signed scope, a purchase order number, or an email where you said go ahead | Do not pay. An unordered bill is either a mistake, a misdirected invoice, or a solicitation dressed as one |
| 2 | Is the sender someone you do business with? | A name you recognise, an email domain that matches the one you have always used, bank details that match last time | Stop. Changed payment details are the single most expensive failure on this list |
| 3 | Is this an invoice at all? | The word Invoice, an invoice number, an amount due and a due date | A proforma, quote or "renewal notice" creates no debt. File it; do not pay it |
| 4 | Do the numbers add up? | Quantity × rate per line, the subtotal, the tax, the total — and the rate against what you agreed | Query it before the due date, in writing, with the line number |
| 5 | Is it billed to the right entity? | Your legal business name, not your personal name or a trading name you no longer use | Ask for a corrected invoice. A bill addressed to the wrong entity is a weak deduction record |
| 6 | Have you already paid this? | The invoice number against what you have paid, and the date against a statement you sent back | Duplicates are usually honest — a resend read as a new bill. Reply with the payment date |
| 7 | When is it really due? | A calendar due date, the terms it was agreed on, and any late-fee clause in the footer | If the terms are shorter than you agreed, say so now rather than after a fee is added |
Checks 1 and 2 are the ones worth slowing down for. Every other failure on the list costs you a corrected PDF and an awkward email. Those two cost you the money.
How to Tell a Fake Invoice From a Real One
Invoice fraud works because a bill is the one piece of unsolicited mail a business is supposed to act on. Three patterns account for most of it, and they need different responses.
1. The bill for something you never bought
A charge appears for antivirus software, a subscription renewal, a cryptocurrency purchase or a "support plan" you do not have, usually for an oddly specific amount — $445.67 rather than $450 — with urgent wording and a phone number to call if you did not authorise it. The invoice is the bait and the phone number is the trap: calling it connects you to the people who sent it, and the "refund" they walk you through is how the money leaves.
Response: do not call the number on the document, ever. If you genuinely think you might have a subscription with that company, open your own records or log into the account directly. Then delete it.
2. The solicitation shaped like an invoice
A domain renewal notice from a registrar you do not use, a business directory listing, a trademark "publication fee", an equipment service contract. These are usually legal, because somewhere on the page — often in small type at the bottom — is a line saying it is a solicitation and not a bill. They are designed for the person in a business who pays what arrives.
Response: check the small print before you assume it is fraud, then apply check 1. If you did not order it, you do not owe it.
3. The real supplier, the wrong bank details
This is the costly one. A genuine invoice arrives from a supplier you really use, for work they really did, with an amount you really owe — and the bank account on it has changed. Sometimes the email account was compromised; more often the message is a near-perfect copy from a lookalike domain, one letter off from the real one. Nothing about the document is wrong except the twelve digits that matter.
Response: treat any change of payment details as unverified until you have confirmed it by voice, on a phone number you already had — from a previous contract or your own contacts, never the number printed on the new invoice. Say out loud what the new account is and have them confirm it back to you. This takes ninety seconds and it is the only control that reliably works.
The one rule worth memorising: bank details never change by email. Not for you, and not for anyone who invoices you. If a supplier's account has moved, that is a phone call — and you place it, to a number you already had.
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Before You Pay a Contractor: the W-9 Step Most People Miss
If the invoice is from an individual or an unincorporated business doing work for your business in the United States, there is paperwork that belongs before the payment, not after it. You need their taxpayer information on a Form W-9 so you can file an information return for the year — and the moment you have leverage to get it is while they are still waiting to be paid.
Chasing a W-9 the following January, from a contractor who finished the job in March and has since moved on, is one of the small miseries of running a business. Ask for it with the first invoice, every time, and keep it on file. The IRS publishes the form and its instructions on the About Form W-9 page; our W-9 glossary entry covers what a contractor should put on it.
Two things to be careful about. First, there is a dollar threshold below which you do not have to file, and that threshold changed for payments made in 2026 — do not work from a figure you memorised years ago, and confirm the current amount and the filing deadline with the IRS or your accountant before you file. Second, the rules differ for payments to corporations, for goods rather than services, and for amounts paid through a card or third-party network, which are reported by the processor instead of by you. When the amounts are meaningful, ask; the cost of asking is an email.
What to Send Back: Four Replies
Silence is the worst response to an invoice, including one you dispute. A supplier who hears nothing assumes the bill is fine and starts a reminder sequence; a supplier who hears "we have it, here is what is happening" waits. These four cover almost everything.
Acknowledging that an invoice was received
Worth sending whenever the amount is large, the supplier is new, or the terms are short. It stops a reminder before it is written and it fixes the date the clock started.
Hi [Name] — confirming we've received invoice [number] for [amount], dated [date]. It's gone into our payment run and is scheduled for [date]. If anything about that doesn't match your records, let me know this week.
Querying a line before the due date
Be specific and name the line. A vague "this looks high" reads as a delaying tactic; a line number reads as a correction request and usually gets one by return.
Hi [Name] — one query on invoice [number] before we pay it. Line [3] shows [8 hours at $X]; our note from [date] has [6 hours]. Could you confirm which is right and send a corrected invoice if needed? The rest of the invoice is approved and we'll pay the full corrected amount on [date].
Approving part of it now
If one line is in dispute and the rest is not, pay the rest. Holding an entire invoice over one disputed line is how a supplier relationship turns into a collections problem.
Hi [Name] — we've paid [$X] of invoice [number] today, covering lines [1–4]. Line [5] is on hold pending [the question above]; as soon as that's settled we'll clear the balance in the same week.
Replying to a payment reminder when you cannot pay yet
A reminder is not an accusation, and the reply that works is not an apology — it is a date. Give the specific day you will pay, give an amount, and then hit that date. Suppliers plan around dates; they cannot plan around "soon".
Hi [Name] — thanks for the reminder, and apologies this has run past the due date. Invoice [number] is approved on our side; the delay is cash timing, not a dispute. I can pay [$X] on [specific date] and the balance on [specific date]. If that doesn't work for you, tell me and we'll find something that does.
Three rules make that reply land. Confirm the invoice is not in dispute, so the supplier stops wondering whether they are about to argue. Name a real date you are confident of rather than an optimistic one. And if the date slips, write before it passes — a moved date that you announce costs you nothing, and a missed date you go quiet on costs you the benefit of the doubt on every future invoice. If a late fee was set out in the original terms, ask about it directly rather than hoping; a supplier who has been told a date will usually waive it, and one who has been ignored will not.
After You Pay: What to Keep
The invoice is not proof of payment. It proves what was asked for. Proof that you paid it is the bank record, the card statement line or the payment confirmation — and a deduction is supported by the pair, not by either one alone. This is the same distinction running the other way round when you are the one billing, and it is worth being precise about: see invoice vs receipt if you have been filing the two interchangeably.
So keep three things together for every bill you pay: the invoice PDF, the payment record, and — for anything that is not obvious from its own description — a line about what it was for. A $600 charge from a hardware supplier is a business deduction or a personal purchase depending on a fact that appears nowhere on the document. Write the purpose down at the moment you file it, because you will not remember in April.
How long to keep it depends on the return it supports; the IRS sets retention by the period of limitations for the return in question, and its recordkeeping guidance is the place to check your own situation rather than a rule of thumb. Whatever period applies, a folder per year and a filename that carries the supplier name, the invoice number and the date will make the difference between an hour and an afternoon if anyone ever asks.
The Same Checklist, Running Backwards
Every one of the seven checks is also a reason your own invoice sits unpaid — and reading them from the other side is the most useful thing on this page.
- No reference to what was agreed (check 1) — the person approving it cannot find the authorisation, so they ask, and the ask takes three days. Quote the PO number or the agreement date on the invoice.
- New sender, new details (check 2) — a first invoice from an unfamiliar address with bank details in the body is the exact shape of the fraud above. Send it from the address you have always used, and mention the details on a call if they are new.
- Not obviously an invoice (check 3) — the word Invoice, a number and an amount due are what makes a document routable. The seven zones of an invoice layout exist precisely so a stranger can process it without reading it.
- Arithmetic that has to be checked (check 4) — every line the payer has to recompute is a chance to delay. Show quantity, rate and line total so the sum is visible rather than implied.
- Wrong entity (check 5) — bill the legal entity, not the person who hired you. This is the single most common reason finance departments bounce an invoice back.
- No unique number (check 6) — without one, nobody can tell your resend from a second bill, and a duplicate-payment scare gets your invoice held while they work it out. Every invoice created in InvoiceBloom is assigned a unique number automatically, which removes this one from the list.
- "Net 30" and nothing else (check 7) — a term with no calendar date makes the payer do arithmetic, and they will do it in their favour. Write the due date as a date; the Net 30 guide covers how the count actually runs.
Read that list once before you send your next invoice and you will have removed most of the reasons a careful payer would put it aside — which is the whole of what you control about how fast you get paid.
Frequently Asked Questions
I received an invoice I did not order. Do I have to pay it?
No. An invoice is a request for payment, and a request creates no obligation on its own — what obliges you is the agreement behind it. If you did not order the goods or services, did not sign anything, and cannot find an acceptance in your records, you do not owe the money. Reply once in writing saying you have no record of an order and are not paying, keep a copy, and stop engaging after that. Unordered merchandise and solicitations disguised as bills are a recognised category of business mail, which is why many of them carry a line in small type admitting they are not a bill.
What does it mean to acknowledge an invoice was received?
It means replying to confirm the bill arrived, that you can see it, and when it is scheduled to be paid — nothing more. It is not an approval of the amount and it does not waive your right to query a line later, though it is good practice to say so if a query is coming. Acknowledgement is worth sending on large invoices, first invoices from a new supplier, and anything on short terms, because it stops a reminder sequence before it starts and it settles when the clock began if anyone later disagrees about the due date.
How do I know if an invoice is fake?
Work backwards from your own records rather than forwards from the document, because a convincing fake looks correct in every respect a document can look correct. Ask whether you ordered this, whether the sender's email domain is character-for-character what you have used before, and whether the payment details match what you paid last time. Two shapes account for most losses: a bill for a product or subscription you do not have, carrying a phone number to call about an unauthorised charge, and a genuine supplier's invoice with changed bank details. Never call a number printed on a suspicious invoice, and never accept a change of bank details that arrives by email without confirming it by voice on a number you already had.
What do I do if I receive a duplicate invoice?
Reply with the evidence rather than ignoring it, because most duplicates are a supplier resending rather than double-billing. Give them the invoice number, the date you paid, the amount and the method, and ask them to confirm it is matched on their side. If it turns out you did pay twice, ask for a refund rather than a credit note unless you are certain of more work with them, and check the invoice number before you pay anything with a number you have seen before — that comparison is why unique invoice numbers exist.
How should I reply to a payment reminder email?
Reply the same day, and lead with a date rather than an apology. Confirm you have the invoice, say whether it is approved or in dispute, and give a specific calendar date you will pay — with an amount if you are paying in parts. A reply that commits to a date lets the supplier plan and almost always stops the escalation; a reply that says "soon" does not, and silence guarantees the next reminder is firmer. If the delay is cash timing rather than a disagreement, say that explicitly, because the two get very different treatment. If a late fee is in the original terms, raise it yourself and ask whether it will be applied — asking usually gets it waived, and not asking never does.
Do I need a W-9 before I pay a freelancer?
If they are a US-based individual or unincorporated business doing work for your business, get one — and get it before the payment rather than after, when you still have a reason for them to send it. You need the name and taxpayer identification number on it to file the year-end information return. The dollar threshold that triggers filing changed for payments made in 2026, and the rules are different for corporations, for goods, and for amounts paid through a card or third-party payment network, so confirm the current figure and your own case with the IRS or your accountant rather than a number you remember.
Is an invoice proof that I paid?
No — it is proof of what was asked for. Payment is proved by the bank or card record, or a receipt from the supplier acknowledging the money arrived. Keep the two together: the invoice establishes what the expense was and why, the payment record establishes that it left your account, and a deduction is supported by the pair. This is exactly the distinction between an invoice and a receipt, and it is the one most small businesses blur when they file.
The Short Version
Seven checks before money moves: did you order it, is the sender genuine, is it actually an invoice, does the arithmetic hold, is the entity right, have you paid it already, and when is it truly due. Bank details never change by email. Get the W-9 before you pay, not in January. Reply to everything — an acknowledgement, a query with a line number, a partial payment, or a date you will hit — because silence is the only response that makes things worse. Keep the invoice and the proof of payment together with a note of what it was for. And read the seven checks backwards now and then: they are the same seven reasons somebody is sitting on yours.