How to add sales tax to an invoice, step by step

To learn how to add sales tax to an invoice, first confirm you are required to collect it, then look up the rate for the sale, apply it only to taxable items, show the tax as its own line, and add it to the total. Keep a record of the rate you used.

This is general information, not legal or tax advice.

First, decide whether you must collect sales tax

Adding the tax is the easy part. Deciding whether the sale is taxable at all is where mistakes happen. In the United States, sales tax is set by states and, in many places, by local governments, not by the federal government. There is no single national rate or rulebook, so what applies to you depends on three questions.

Do you have nexus in that state?

Nexus is a connection between your business and a state that is strong enough for the state to require you to collect its sales tax. Traditionally, it meant a physical presence, such as an office, a warehouse or employees. In 2018, the US Supreme Court decided in South Dakota v. Wayfair that a state may require a seller with no physical presence to collect tax. The case concerned South Dakota’s law, which applied to sellers delivering more than $100,000 of goods or services into the state in a year, or making 200 or more separate transactions into the state.

Since then, many states have adopted their own economic nexus thresholds, and the numbers differ. So the practical rule is this: you may owe sales tax in the state where you work and in other states where your sales pass that state’s threshold. Check each state’s revenue department for its current rules before you assume you are in or out.

Is what you sell taxable there?

States tax different things. Many tax most physical goods and exempt many services, but there are exceptions in both directions, and the details vary by state and by item. A freelancer who sells only consulting hours may collect nothing in one state and something in another. A contractor who sells materials may need to charge tax on the materials but not on labor, or the other way around. Look up your state’s guidance for your trade rather than guessing.

Is the buyer exempt?

Some buyers do not pay sales tax: resellers buying goods to sell again, certain nonprofits, and government bodies in many states. A buyer claims this with an exemption or resale certificate. If you do not have the certificate on file, a state may hold you liable for the tax you should have collected. Ask early and keep a copy.

If you need a fast estimate while you work this out, the free sales tax calculator applies a rate you enter and shows the tax and total.

Find the right rate

Once you know the sale is taxable, you need the rate. Some points to keep in mind:

• State rate plus local rates. In many states, cities, counties or special districts add their own tax on top of the state rate. The combined rate depends on the address.
• Destination or origin. Some states charge the rate where the customer is. Others charge the rate where the seller is. Your state’s guidance says which one applies.
• Rates change. Re-check at least once a year, and again when you start serving a new area.
• Use official sources. Your state department of revenue or taxation publishes rates, and many offer lookup tools.

Some states work together through the Streamlined Sales and Use Tax Agreement, which is run by the Streamlined Sales Tax Governing Board and aims to simplify and modernize how states administer sales tax. The Board’s own site lists which states take part. Membership does not make the rate the same across states, but it can make registration and rules more uniform.

Write down the rate you used and where you found it. If you are ever audited, “I used 7% because the state’s lookup tool said so on this date” is a good answer.

Add the tax to the invoice in five steps

Label the line clearly, for example “Sales tax (7%)”. Do not bury it in a unit price, because the customer and your bookkeeper both need to see it separately. If you operate in more than one state or need to show state and local tax separately, add a line for each.

Line-level versus invoice-level tax

You can calculate tax on each line or once on the taxable total. Both are common, and they can differ by a cent or two because of rounding.

Suppose an invoice has three small items at $0.99 each, and the rate is 8.25%.

• Line by line: each line has tax of 0.99 times 0.0825, which is $0.0817, rounded to $0.08. Three lines give $0.24.
• On the total: the subtotal is $2.97, and 2.97 times 0.0825 is $0.2450, rounded to $0.25.

Same invoice, a one cent difference. Neither is wrong in itself. Your state may say which method to use, and some say tax should be computed on the invoice total. Pick the method your state’s guidance supports and use it every time. If an invoice has both taxable and exempt lines, line-level marking is clearer, because it shows exactly which items carried tax.

The mini invoice below applies a flat rate across the whole invoice, so it shows the simpler case where every line is taxable, at the same 7%:

Here the subtotal is $300.00, tax at 7% is $21.00, and the total is $321.00. The invoice generator can build this kind of invoice for you, and the sales tax calculator lets you test the numbers first.

What to show on the invoice

Put the following on any invoice that includes sales tax:

• Your business name and address
• The customer’s name and address
• An invoice number and date
• Each item with quantity, unit price and line total
• A clear note on which lines are taxable and which are exempt, if mixed
• The tax rate and the tax amount, on a separate line
• The total due and the payment terms
• Your sales tax permit or registration number if your state asks you to show it
• A reference to the customer’s exemption certificate, if one applies

For a fuller list, see what to include on an invoice.

Collecting, reporting and paying

Collecting the tax is only the first step. Sales tax belongs to the state, and you hold it until you file.

• Register first. Most states require a seller’s permit or sales tax registration before you collect tax. Collecting tax without being registered can cause problems.
• Keep it separate. Do not treat collected tax as income. Some businesses move it into a separate account on the day the invoice is paid.
• File on schedule. States assign monthly, quarterly or annual filing, often based on volume. Missing a return can bring penalties and interest.
• Report invoices that were not paid. Rules on bad debt and tax you already remitted vary by state.
• Keep records. The IRS says invoices are evidence of your gross receipts and that you should keep supporting documents that show the amounts and sources of your receipts. For federal income tax, the IRS says the default period to keep records is 3 years, with longer periods in some cases. State sales tax record rules can differ, so check yours.

Common mistakes

• Charging tax when you do not have to. Collecting tax you do not owe can create a duty to remit it. Confirm the rules first.
• Not charging tax when you do. You may be liable for the uncollected amount, and you cannot easily bill customers for it later.
• Using one rate everywhere. Local rates and destination rules can change the rate by address.
• Taxing shipping or labor wrongly. Whether delivery charges and labor are taxable varies by state.
• Forgetting exemption certificates. A verbal “I’m exempt” is not enough.
• Hiding tax in the price. If you quote a tax-inclusive price, still show the tax portion on the invoice.
• Switching rounding methods. Pick one and keep it.

A checklist for every taxable invoice

• I confirmed the sale is taxable in this state, or I have an exemption certificate on file.
• I registered with the state before collecting tax.
• I found the rate for the delivery or service address and noted the source and date.
• I marked each line taxable or exempt.
• I calculated tax with the same rounding method I always use.
• Tax appears on its own line with the rate named.
• The invoice has a number, date, items, totals and terms.
• I saved a copy of the invoice and any exemption certificate.

Where PayToMe fits

PayToMe is in public beta: you can sign in at app.paytome.si, create invoices, send them and get paid. You can save tax rates and mark one as the default so it is applied to new invoices; country-aware checks before you send are in development. For quick checks there is the free sales tax calculator, and the invoice generator builds and downloads the invoice. If you are still learning the basics, start with how to write an invoice, and see the sales tax glossary entry for definitions.

Sources

• South Dakota v. Wayfair, Inc., decided June 21, 2018: the Supreme Court overruled the physical presence rule and described South Dakota’s $100,000 or 200-transaction law.
• Streamlined Sales Tax Governing Board: describes the Streamlined Sales and Use Tax Agreement and its aim to simplify state sales tax administration.
• IRS, What kind of records should I keep and How long should I keep records.
• Your state department of revenue or taxation is the authority on rates, taxable items, permits and filing dates. We do not list state rates here because they change.

This is general information, not legal or tax advice.