How to Read an Invoice: Sample, Totals and Red Flags

How to read an invoice: start at the top to confirm who sent it and who it's billed to, then check the invoice number, dates and line items against what you actually ordered or received. Then work down the totals to the balance due, and pay that amount by the due date using payment details you have confirmed are genuine.

This guide is for anyone checking a bill: a client or office admin working out what they owe, or a small business checking a supplier's invoice before paying it.

How to read an invoice, part by part

Most invoices follow the same layout: who it's from and to at the top, reference numbers and dates next, what was supplied in the middle, and totals and payment instructions at the bottom. Read it in that order.

Here's a sample invoice. The businesses, numbers and addresses are made up for this example. The numbers in brackets match the table below it.

[1] INVOICE (sample only, fictional businesses)
[2] From	Maple & Pine Design LLC (fictional), 100 Example Ave, Anytown, TX 00000, billing@example.com
[3] Business ID	Tax ID shown by the seller (in Australia this would be an ABN)
[4] Bill to	Harbor Dental Group (fictional), Attn: Accounts Payable
[5] Invoice number	INV-0147
[6] Invoice date	October 1, 2026
[7] Terms / due date	Net 30 / October 31, 2026
[8] PO number	PO-55210

[9] Description	Qty	Rate	Amount
Website maintenance, September	10 hrs	$85.00	$850.00
Hosting plan, annual	1	$240.00	$240.00
Printed brochures (taxable)	500	$0.42	$210.00
[10] Subtotal			$1,300.00
Discount: 10% off maintenance			–$85.00
Sales tax 8% on taxable items ($210.00)			$16.80
Total			$1,231.80
[11] Amount paid (deposit, September 2)			–$400.00
Balance due			$831.80

[12] Payment details: bank transfer or card via the payment link. [13] Notes: "Please quote INV-0147 with your payment."

#	Field	What it tells you	What to check
1	Document title	That this is a bill, not a quote or receipt	A quote isn't a request to pay; a receipt means it's already paid
2	Seller details	Who is asking to be paid and how to contact them	The name matches a supplier you actually deal with, and the contact details match your records
3	Business ID	The seller's tax or business registration number	In Australia, an ABN you can look up for free
4	Bill to	Who the seller thinks owes the money	It's your business (or the right branch or department), not someone else's
5	Invoice number	The unique reference for this bill	You haven't already paid this number. Quote it when you pay.
6	Invoice date	When the invoice was issued	It's after the work or delivery; terms count from it
7	Terms and due date	When payment is due	The terms match what you agreed (for example Net 30, not due on receipt)
8	PO number	Which purchase order this invoice relates to	The PO exists, is approved, and hasn't already been fully billed
9	Line items	What you're being charged for, how many, at what price	Quantities match what arrived; rates match the quote or PO
10	Subtotal, discount, tax, total	How the price was built up	The maths adds up and tax is only on items that should carry it
11	Amount paid and balance due	What's already been paid and what's left	Your deposit or earlier payment has been credited
12	Payment details	Where and how to pay	Bank details match ones you've confirmed before (see red flags)
13	Notes	Payment references, late fees or other terms	Any late fee or interest is something you agreed to

How to read the totals on an invoice

Read the totals block from top to bottom: subtotal, then any discount, then tax, then the invoice total, then any amount already paid, and finally the balance due. The balance due is the number you pay; the total is what the whole job cost.

Here's how the sample invoice adds up:

Subtotal: $850.00 + $240.00 + $210.00 = $1,300.00. This is every line item before discounts and tax.
Discount: 10% off the maintenance line only: 10% × $850.00 = –$85.00. Check what the discount applies to. A "10% discount" on the whole subtotal would have been $130.00.
Tax: the seller has marked only the brochures as taxable, so 8% × $210.00 = $16.80. Taxability depends on where you are, so query any line that looks wrong.
Total: $1,300.00 – $85.00 + $16.80 = $1,231.80.
Amount paid: the $400.00 deposit paid in September = –$400.00.
Balance due: $1,231.80 – $400.00 = $831.80. This is what you pay by October 31.

Every time, redo the line maths yourself (quantity × rate), since 50 hours instead of 5 is easy to miss if you only look at the total. Then confirm any deposit appears under "amount paid"; if it doesn't, you'd pay it twice.

If the invoice is wrong, don't just short-pay it. Ask the seller to reissue it or send a credit note for the difference, so both sets of books agree.

How to read payment terms and dates

An invoice usually shows two dates: the invoice date (when it was issued) and the due date (when payment must arrive). Payment terms such as "Net 30" tell you how the due date was worked out, counted from the invoice date unless the terms say otherwise.

Term on the invoice	What it means	Sample: invoice dated October 1, 2026
Due on receipt	Pay as soon as you receive it	Due October 1
Net 7	Full amount due 7 days after the invoice date	Due October 8
Net 14	Full amount due 14 days after the invoice date	Due October 15
Net 30	Full amount due 30 days after the invoice date	Due October 31
2/10 Net 30	Take 2% off if you pay within 10 days; otherwise the full amount is due in 30	2% off if paid by October 11; full amount by October 31*
EOM / Net 30 EOM	Counted from the end of the month the invoice is dated	Net 30 EOM: due November 30

*Check what the 2% comes off. On the sample, 2% of the $831.80 balance is $16.64, but 2% of the $1,231.80 total is $24.64, so the amount you pay differs by $8. If the invoice doesn't say, ask before you take the discount. To count the exact day for any term, use the invoice due date calculator, and for what Net 30 means for each side, see Net 30 payment terms.

If the terms differ from your agreement (your contract says Net 30, the invoice says due on receipt), ask for a corrected invoice rather than rushing a payment.

How to read a purchase order invoice

A purchase order invoice is a supplier's bill that quotes the purchase order (PO) number your business issued when it placed the order. To read one, match it against two other documents: the PO (what you agreed to buy, at what price) and the receiving record or delivery docket (what actually arrived). This check is called a three-way match.

Check	Purchase order PO-55210	Delivery record	Invoice INV-0147	Result
Item	Printed brochures	Printed brochures	Printed brochures	Match
Quantity	500	480 received	500 billed	Query: 20 short
Unit price	$0.42	n/a	$0.42	Match
Line amount	$210.00	n/a	$210.00	Should be $201.60 for 480

In this example the price and description match, but the delivery came up 20 brochures short. The supplier is billing for 500, so either the missing 20 are on their way or the invoice should be reduced by 20 × $0.42 = $8.40, plus the 8% tax on that amount ($0.67), a $9.07 difference. You'd hold that line (or the whole invoice, depending on your process) and ask the supplier.

Also check that the PO number is quoted exactly and that the PO hasn't already been fully billed by an earlier invoice. If you're the one sending invoices to a company that uses POs, here's how to invoice against a purchase order so yours gets paid on the first pass.

How to read a tax invoice in Australia

An Australian tax invoice is the GST version of an invoice, and you need one from your supplier to claim a GST credit on a purchase that costs more than A$82.50 (including GST). To read one, check that it's clearly a tax invoice, shows the seller's ABN, and shows the GST, and for sales of A$1,000 or more, that it names you as the buyer.

According to the ATO's tax invoice requirements (checked November 2026), a tax invoice for a sale under A$1,000 must include enough information to work out seven things:

That the document is intended to be a tax invoice
The seller's identity
The seller's ABN
The date it was issued
A brief description of what was sold, including quantity (if applicable) and price
The GST amount, shown separately or, if GST is exactly one-eleventh of the total, a statement that the "total price includes GST"
The extent to which each item is a taxable sale

For sales of A$1,000 or more, it must also show the buyer's identity or ABN. Example: a supplier bills you A$1,320 including GST. GST is one-eleventh, so A$1,320 ÷ 11 = A$120. Because the sale is over A$1,000, your business name or ABN must appear on it; if it doesn't, ask for a corrected invoice.

If you ask for a tax invoice, the supplier must provide it within 28 days, unless the sale is A$82.50 (including GST) or less. An invoice with incorrect or incomplete information is not a valid tax invoice, though you may be able to treat it as one if the missing details are on other documents from the supplier (ATO: when you can claim a GST credit). And a tax invoice emailed as a PDF counts, as long as it contains all the required information.

To check the ABN, use the free ABN Lookup, which shows the business type and GST status. If an invoice charges GST but ABN Lookup shows the business isn't registered for GST, query it before paying. There's more on the required fields in what is a tax invoice.

Red flags to check before you pay an invoice

Before paying, check three things: that the bank details haven't changed, that you haven't paid this invoice number before, and that the business identifying details are present and real.

Changed bank details. In a fake invoice scam, a criminal sends an invoice that looks like it's from a real supplier but carries their own bank account. The IRS describes this as a form of business email compromise and cites FBI figures that these fake invoice scams resulted in an average loss of over $120,000 (IRS, National Tax Security Awareness Week). Australia's business.gov.au advises being cautious if someone asks you to send money to a new bank account or change payment details at short notice, and to verify the request directly with the business using contact details you already know and trust. Phone the supplier on a number from your own records, not one on the invoice or email, before paying new bank details. If money has already gone, contact your bank immediately.

Duplicate invoice numbers. Every invoice should have its own invoice number. If you've already paid INV-0147, a second INV-0147 is either a resend (so don't pay it again) or a mistake. Search your records by number and by amount, since a duplicate can carry a new number with the same total.

Missing business ID. If an Australian supplier doesn't quote an ABN, the ATO says the payer may need to withhold 47% of the payment under "no ABN withholding", unless an exception applies, such as payments of A$75 or less excluding GST (ATO: statement by a supplier not quoting an ABN). In the US, businesses that pay contractors usually collect a Form W-9, which the IRS describes as the form used to provide a correct Taxpayer Identification Number to the person who has to file an information return, such as a 1099 (IRS: about Form W-9).

Other signs worth a second look:

An invoice for something you don't remember ordering, or from a supplier you've never used
Pressure to pay immediately, or a threat that your account will be suspended
A request to pay in an unusual way, such as gift cards
A sender email address that's one letter off from the supplier's real domain

Once you've paid, keep the invoice. The IRS lists invoices among the supporting documents a business should keep for its books and tax return.

If you also send invoices, your clients check these same fields on yours. Make an invoice with InvoiceSonic's free invoice generator: no sign-up needed to download a PDF, and it lays out the invoice number, dates, terms, line items and totals in the order clients read them. Payment goes straight to your own account, so InvoiceSonic takes 0% of it.

Frequently asked questions

What is the most important number on an invoice?
The balance due. It's the invoice total minus anything you've already paid, such as a deposit, and it's the amount you actually owe by the due date. If there's no "amount paid" line, the balance due and the total are the same.

What's the difference between the invoice date and the due date?
The invoice date is when the invoice was issued. The due date is when payment must arrive, usually worked out from the invoice date using the payment terms: on Net 30, an invoice dated October 1 is due October 31.

What does "due on receipt" mean on an invoice?
It means the seller expects payment as soon as you receive the invoice, with no grace period. If you agreed to different terms in a contract or quote, ask the seller to correct the invoice before you pay.

What is a PO number on an invoice?
It's the purchase order number your business issued when it placed the order. The supplier quotes it so your accounts team can match the invoice to the approved order and to the delivery record before paying.

How do I know if an invoice is a valid tax invoice in Australia?
It must be clearly intended as a tax invoice and show the seller's identity and ABN, the issue date, what was sold with quantity and price, the GST, and which items are taxable. Sales of A$1,000 or more must also show the buyer's identity or ABN.

What should I do if a supplier's invoice has new bank details?
Don't pay until you've confirmed the change by phoning the supplier on a number from your own records, not one from the invoice or email. Changed bank details are the core of fake invoice scams. If you've already paid, contact your bank immediately.