What Must Be on a US Invoice: Sales Tax Lines and Numbering

The short answer: no federal invoice format applies

There is no single federal law that tells a US business what its invoice must look like. The Internal Revenue Service does not publish an invoice template. Its rules come from recordkeeping. IRS Publication 583, Starting a Business and Keeping Records, explains that the law generally does not require a specific kind of record, but that your system must clearly show your income and expenses. Your invoices are part of the supporting documents behind those numbers.

Sales tax is the other source of rules, and it is set state by state and sometimes locally. Some states go further than the IRS. Washington law, cited by the Washington Department of Revenue, requires sellers to state the retail sales tax separately on invoices and other sales documents. New York's Department of Taxation and Finance says sellers must always separately state the amount of sales tax due on the invoice or receipt given to the customer. If a state requires that line, leaving it out is a compliance problem, not a formatting choice.

So the practical answer has two parts. Use a clear, consistent invoice that supports your books. Then check your state's sales tax rules to see whether tax must appear as its own line.

The fields most businesses need on every invoice

A federal format does not exist, but a working invoice needs the same core information in almost every case. The table below lists the fields, what each one does for you, and where the requirement comes from.

You do not need a special layout for any of this. A spreadsheet or invoicing tool that prints these fields on one page works for most businesses. The key habit is consistency. Use the same layout each time, so a reader or an auditor can find the same information on every document.

How to work out the sales tax line, step by step

The tax figure is simple arithmetic once you know which items are taxable and what rate applies. The rate and the taxability rules come from your state revenue department, and in many places from a local rate on top of the state rate.

1. Split the invoice into taxable and non-taxable lines. Mark each line as one or the other before you add anything up.
2. Add up the taxable lines to get the taxable subtotal. Add the non-taxable lines separately, so the invoice shows both figures if the state expects that.
3. Look up the combined rate that applies where the sale takes place. Use your state revenue department's rate tables, and check whether a local rate applies.
4. Multiply the taxable subtotal by the rate and round to the cent.
5. Add the tax line to the subtotal to get the total due. Show the rate, the taxable base and the tax amount so the buyer can check them.

Two details trip people up. The first is the order of discounts and tax. Apply the discount before you calculate the tax, unless your state rules say otherwise. The second is the taxable base. If only part of the invoice is taxable, the tax line must be calculated on that part alone.

Worked example: a mixed invoice with real numbers

Imagine a small bookkeeping firm in Washington that bills a client for monthly bookkeeping and also supplies a printed reporting binder. Assume, for this example only, that both lines are taxable and that the combined rate is 8.0 percent. Your actual rate will differ, and the rate and taxability depend on the buyer's location and your state's rules, so confirm them with the Washington Department of Revenue before you copy these figures.

The invoice number could be INV-2026-0142, the issue date 30 June 2026, and the payment terms net 30 days. Each line sits on its own row, and the sales tax appears as a separate line with its rate. If the binder were non-taxable in your state, the taxable subtotal would fall to 1,500.00, the tax would be 120.00, and the total would be 1,620.00. That one change shows why the line-by-line split matters.

Cases that change the answer

The basic fields stay the same, but several situations change what the invoice has to show.

Mixed taxable and non-taxable items. New York's rules say that if you sell both taxable and non-taxable goods or services, you must identify which items are taxable on the invoice or receipt. The same idea applies in other states that tax some items and not others.

Items packaged for one price. New York's guidance gives a clear case. If items are packaged together for one price and cannot be sold separately, tax is charged on the whole price, even if one part would be exempt on its own. Splitting a bundle onto separate lines does not help unless the items really are sold separately.

Fixed-price contracts and hourly billing. A fixed-price invoice may be issued for a milestone rather than for hours worked. Keep the contract reference on the invoice so the amount can be traced back to the agreed terms. Whether the milestone is taxable depends on what it delivers, not on how the invoice is titled.

Retention periods. The IRS says in its newsroom guidance that it generally suggests keeping records for three years. Publication 583 adds that you must keep records as long as they may be needed for the administration of any provision of the Internal Revenue Code. Employment tax records must be kept for at least four years after the date the tax becomes due or is paid, whichever is later.

Cross-state sales. If the buyer is in another state, the rules of the place where the sale takes place may apply, not only the rules of your home state. Ask your state revenue department how it treats sales to out-of-state buyers before you assume that one rate covers every invoice.

What automation cannot decide. Software can apply a rate you have entered and total the lines. It cannot decide whether a service or product is taxable in a given state, and it cannot know whether a buyer holds a valid exemption. A person who knows your products and your state rules must set those inputs and check them.

Common mistakes

• Folding sales tax into the unit price. Several states require the tax to be shown separately, and an invoice that hides it can fail that test.
• Skipping or reusing invoice numbers. Gaps and duplicates make reconciliation and audits harder. If you cancel an invoice, keep the document and mark it void.
• Writing vague descriptions such as "consulting" or "services". Buyers' accounts payable teams often stall on invoices they cannot match to a contract or purchase order.
• Calculating tax on the wrong base. Tax applied to the full invoice when only some lines are taxable creates an over-collection that the buyer may dispute and that you may have to correct.
• Storing invoices in a way that cannot be retrieved. The IRS expects records to be available for inspection, so keep electronic copies in a system you can search and print.

What to check with your state, HR or a lawyer

Start with your state revenue department. Its site should give the current rates, the taxability rules for your type of product or service, and any rule on how tax must appear on the invoice. Then read IRS Publication 583 for the record keeping side, and check the recordkeeping guidance on the IRS newsroom page. If your business has employees, the employment records rules in the same publication apply to payroll documents too.

Ask an accountant or a tax lawyer when the answer depends on facts you cannot settle yourself. Examples include multi-state sales, a product that might be exempt, a buyer that claims an exemption, or an invoice tied to a government contract. This explains the rule in general terms; it is not legal or tax advice for your case.

Where routine invoice work can run automatically

Many businesses rebuild invoices by hand each month. Employers who want to take that routine work off staff can have AI workers pull billing data from the system of record, apply the invoice numbering sequence, and fill the fields described above. The same workers can flag lines that lack a tax category and route the draft to a person for approval. The person still decides taxability, checks the rate against the state revenue department's tables, and signs off before the invoice is sent. The same approach can handle follow-ups on unpaid invoices and the monthly reconciliation of invoices against bank receipts.