Purchase Invoice vs Sales Invoice: Differences and Examples
Purchase invoice vs sales invoice explained: who issues each, how they hit payables and receivables, a worked example and a checklist for recording both.
Quick answer: In the purchase invoice vs sales invoice comparison, the document is the same but the viewpoint differs. A sales invoice is issued by the seller and recorded as revenue and accounts receivable. A purchase invoice is that same invoice in the buyer's books, recorded as an expense or asset and accounts payable.
Small business owners run into both every week. You send invoices to customers, and suppliers send invoices to you. Because the same piece of paper (or PDF) plays a different role depending on which side of the deal you are on, the terms get mixed up in conversation, in software menus and even in some online guides. This article lays out the difference clearly, with a side-by-side table, a worked example showing how one transaction lands in two sets of books, a checklist for handling each type and the mistakes that cause the most trouble.
If you mainly want to understand the document you send to customers, our guide to what a sales invoice includes covers its fields in detail. Here we focus on how the two sides compare.
Purchase invoice vs sales invoice: the core difference
An invoice is a request for payment. It lists what was supplied, the price, any tax and the payment terms. Who calls it what depends on the direction of the money:
- Sales invoice (outgoing): you supplied goods or services and you are asking a customer to pay. It increases your revenue and the money owed to you.
- Purchase invoice (incoming): a supplier delivered something to you and is asking you to pay. It increases your expenses or assets and the money you owe.
So when a print shop sends a bakery an invoice for menus, the print shop files it as a sales invoice and the bakery files the very same document as a purchase invoice. Nothing about the content changes; only the accounting treatment does.
A lot of software sidesteps the confusion by calling incoming documents "bills." If you have read our explainer on the difference between an invoice and a bill, you will recognize the pattern: a purchase invoice and a supplier bill are, for most purposes, the same thing.
Who issues a purchase invoice?
This is where online sources disagree. In standard usage the supplier issues the invoice and the buyer records it as a purchase invoice. The buyer does not create anything new; it receives, checks and posts the supplier's document.
There is one genuine exception. Under a self-billing arrangement, the customer prepares the invoice on the supplier's behalf, usually because the customer knows the final quantities or rates first. Even then, the document is a sales invoice for the supplier and a purchase invoice for the customer. Self-billing normally requires a written agreement, and in VAT countries it comes with extra rules, so do not start doing it informally.
Purchase invoice vs sales invoice: side-by-side table
| Feature | Sales invoice | Purchase invoice |
|---|---|---|
| Direction | Outgoing, sent to a customer | Incoming, received from a supplier |
| Created by | You, the seller | The supplier (or you, under self-billing) |
| Ledger affected | Accounts receivable | Accounts payable |
| Profit and loss effect | Increases revenue | Increases expenses or cost of sales (or an asset, for equipment) |
| Typical double entry | Debit receivables, credit sales | Debit expense or inventory, credit payables |
| Invoice number | Your own sequential number | The supplier's number, plus your internal reference |
| Sales tax or VAT | Output tax you collect and pay over | Input tax you may be able to reclaim (VAT/GST systems) |
| Key check before posting | Correct customer, prices and tax | Matches the order and what was received |
| Cash effect when settled | Money comes in | Money goes out |
| Main risk | Late payment by the customer | Duplicate payment or fraud |
How each one flows through your books
The clearest way to see the difference is to follow the ledgers. Sales invoices feed accounts receivable, the running total of what customers owe you. Purchase invoices feed accounts payable, the running total of what you owe suppliers. Our comparison of accounts payable and accounts receivable explains how those two balances behave and how to manage each.
The sales side
When you issue a sales invoice under accrual accounting, you recognize revenue at that point, even though no cash has arrived. Receivables go up. When the customer pays, cash goes up and receivables go down by the same amount. Revenue is not touched again.
The purchase side
When a supplier's invoice arrives, you record the cost and a liability to pay it. If the purchase is something you consume quickly, such as fuel or software, it is an expense. If it is stock for resale, it goes to inventory first. If it is a long-lived item such as a machine, it may be capitalized as an asset and depreciated. When you pay, cash goes down and payables go down.
The exact postings are covered in our guide to writing journal entries, but the pattern is always a mirror image of the sales side.
Worked example: purchase invoice vs sales invoice for one sale
Here is an illustrative example. The figures are made up to show the arithmetic.
Brightline Print sells 500 printed menus to Corner Bakery at $1.20 each, plus a $25 design fee. Sales tax applies at an illustrative 8% on the full amount.
- Menus: 500 × $1.20 = $600.00
- Design fee: $25.00
- Subtotal: $600.00 + $25.00 = $625.00
- Sales tax: $625.00 × 0.08 = $50.00
- Invoice total: $625.00 + $50.00 = $675.00
In Brightline's books (sales invoice):
- Debit accounts receivable $675.00
- Credit sales revenue $625.00
- Credit sales tax payable $50.00
Brightline's revenue rises by $625, not $675, because the $50 of tax belongs to the state and is only being collected on its behalf.
In Corner Bakery's books (purchase invoice):
- Debit printing and marketing expense $675.00 (in a US sales tax setting, the tax is usually part of the buyer's cost)
- Credit accounts payable $675.00
If the same deal happened under a VAT or GST system and the bakery were registered, it would typically post $625 to expense and $50 to an input tax account it can reclaim, subject to local rules.
When the bakery pays 30 days later, both sides clear their balances: Brightline debits cash $675 and credits receivables $675; Corner Bakery debits payables $675 and credits cash $675. The same $675 has moved from one business to another, and both ledgers agree.
What each document should contain
Because they are the same document, the required content is the same. A valid invoice usually shows:
- The seller's name, address and, where required, tax registration number
- The buyer's name and address
- A unique invoice number and the issue date
- A description, quantity and unit price for each line
- Subtotal, tax rate, tax amount and total due
- Payment terms, due date and how to pay
- Any purchase order number the buyer gave you
As a seller, you control this content. You can build a clean sales invoice with our free invoice generator, which creates a PDF in your browser, and use the invoice number generator to keep your numbering sequential. The generator does not track bills you receive or post anything to your books, so purchase invoices still need to go into your bookkeeping system or spreadsheet.
As a buyer, you do not control the content, but you can insist on it. If a supplier's invoice is missing a tax number, a PO reference or a clear description, ask for a corrected copy before you approve it.
Purchase invoice vs purchase order
A frequent mix-up is between a purchase invoice and a purchase order. The order comes first and goes from buyer to supplier; the invoice comes later and goes from supplier to buyer. Our guide to invoices versus purchase orders covers the full sequence. Larger buyers check every incoming invoice against the original order and a receiving record before paying, a control known as three-way matching. Even a small business can borrow the idea: never pay an invoice until someone confirms the goods arrived or the work was done.
Checklist for handling both types
For every sales invoice you send:
- Use the next number in your sequence and today's date
- Copy the customer's legal name and any PO number exactly
- Itemize lines so the customer's team can match them to their order
- Show tax separately and state the due date
- Record it in receivables the day you send it
- Follow up on or just after the due date
For every purchase invoice you receive:
- Confirm the supplier is known and the invoice is not a duplicate
- Match quantities and prices to the order or quote
- Confirm delivery or completion with whoever received the goods
- Check tax calculations and, in VAT systems, the supplier's registration number
- Verify any change in bank details by phone using a number you already hold
- Record it in payables with the supplier's invoice number and a due date
- Store the file so you can find it at tax time
Common mistakes
Recording sales tax as revenue or ignoring reclaimable input tax
Tax collected on a sales invoice is not income. Tax paid on a purchase invoice may be reclaimable under VAT or GST. Posting either to the wrong account distorts both profit and your tax return.
Paying a purchase invoice twice
Suppliers sometimes resend invoices as reminders, and the copy gets processed as a new bill. Always search payables for the supplier's invoice number before approving.
Using the supplier's number as your own sequence
Your sales numbering must be continuous and unique to you. A supplier's numbers belong in a reference field on the bill, not in your sales sequence.
Treating every purchase as an expense
Equipment and other long-lived assets bought on a purchase invoice may need to be capitalized rather than expensed in full, depending on the amount and local tax rules.
Throwing away paper purchase invoices
Purchase invoices support deductions and tax reclaims. Our guide on how long to keep invoices covers retention periods, and the IRS explains why supporting documents matter on its recordkeeping page.
Which one do you need to create?
You only ever create sales invoices, unless you have a formal self-billing agreement. Purchase invoices arrive from suppliers; your job is to check them, record them and pay them on time. Settling the purchase invoice vs sales invoice question in your own workflow comes down to two habits: issue clean, numbered sales invoices promptly, and run every incoming bill through the same short approval check.
For more explainers that put similar documents side by side, browse the comparisons section of the blog.
Frequently asked questions
What is the main difference between a purchase invoice and a sales invoice?
It is the same kind of document seen from opposite sides of a transaction. The seller issues a sales invoice to request payment, and records it as revenue and an amount receivable. The buyer receives that document and records it as a purchase invoice, which becomes an expense or asset and an amount payable. One transaction, one document, two different entries in two sets of books.
Who issues a purchase invoice?
In normal usage the supplier issues it. The buyer simply calls it a purchase invoice because it records a purchase. The main exception is self-billing, where the buyer prepares the invoice on the supplier's behalf under a written agreement, which is common in some industries such as haulage, construction and agriculture. Some software also uses purchase invoice to mean the buyer's internal record of a supplier bill.
Is a purchase invoice the same as a bill?
Practically, yes. Many accounting apps label incoming supplier invoices as bills and outgoing customer invoices as invoices, so a purchase invoice and a bill usually refer to the same thing. The difference is mostly vocabulary. What matters is that the buyer records it in accounts payable, checks it against what was ordered and received, and pays it by the due date.
Is a purchase invoice a debit or a credit?
In double-entry bookkeeping a purchase invoice normally debits an expense, inventory or asset account and credits accounts payable, because the business now owes the supplier. A sales invoice does the reverse on the seller's side: it debits accounts receivable and credits sales revenue. Any sales tax or VAT is posted to its own tax account rather than to revenue or expense.
Is a purchase order the same as a purchase invoice?
No. A purchase order is sent by the buyer before delivery to say what it wants to buy, at what price and on what terms. A purchase invoice arrives from the supplier after goods or services have been delivered and asks for payment. Buyers often match the two, along with a delivery or receiving record, before approving the invoice for payment.
Do I need to keep purchase invoices for tax purposes?
Generally yes. Purchase invoices support the expenses you deduct and, in VAT or GST systems, usually the input tax you reclaim. Tax authorities expect you to keep them for a set period, which differs by country and by situation. In the US the IRS ties retention to the period in which a return can be examined, often three years but sometimes longer. Check the rules where you file.
Can the same invoice number appear on a purchase invoice and a sales invoice?
Yes, because they come from different businesses. Your sales invoices follow your own numbering sequence. A purchase invoice carries the supplier's number, not yours. Many buyers also assign an internal reference to each incoming bill so they can track it, but they should keep the supplier's invoice number on file because that is what the supplier will quote when chasing payment.
What should I check before paying a purchase invoice?
Confirm the supplier is genuine and the bank details match what you have on file, that the goods or services were actually received, that quantities and prices match the purchase order or quote, that tax is calculated correctly, and that the invoice has not already been paid. These checks catch most duplicate payments and invoice fraud attempts before money leaves the account.
Invoice Creator Editorial Team
Guides on invoicing, cash flow and small-business finance from Invoice Creator, operated by Next Software Development Company. Content is reviewed for accuracy against the fields our own invoice generator produces.
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