The sales tax you add to an invoice is the combined state and local rate that applies to the sale, multiplied by the taxable portion of the invoice. Figuring out how much tax to add to an invoice comes down to three questions in order: do you have a legal obligation to collect tax on this sale, is what you’re selling taxable, and what is the combined rate for the applicable address. State-level rates run from 2.9% in Colorado to 7.25% in California, and once county and city taxes stack on top, the combined rate can pass 11% in parts of Louisiana.1Tax Foundation. State and Local Sales Tax Rates, 2026 Get the number wrong and you, the seller, are personally on the hook for any tax you should have collected.
First, Do You Have to Collect Tax on This Sale?
You only charge sales tax when your business has a legal connection to the taxing jurisdiction. The term is nexus, and it comes in two forms.
Physical nexus is the obvious one: an office, a warehouse, an employee, or inventory in a state gives you nexus there. Economic nexus is the trap for remote sellers. After the Supreme Court’s 2018 decision in South Dakota v. Wayfair, Inc., a state can require an out-of-state business to collect sales tax based on sales volume alone.2The CPA Journal. Changing the State and Local Tax Nexus Playing Fields The most common threshold is $100,000 in annual sales into the state. Some states also trigger nexus at 200 or more separate transactions, though the trend is moving away from the transaction count, and a growing number of states have dropped it.3Sales Tax Institute. Economic Nexus State by State Chart
Five states impose no statewide sales tax: Alaska, Delaware, Montana, New Hampshire, and Oregon.1Tax Foundation. State and Local Sales Tax Rates, 2026 For buyers in those states there is generally no sales tax to add, though Alaska is a partial exception because some local jurisdictions there impose their own.
One more carve-out matters. If you sell through a platform like Amazon, Etsy, or eBay, most states with a sales tax have marketplace facilitator laws that shift the collection duty from you to the platform.4Streamlined Sales Tax. Marketplace Facilitator State Guidance The marketplace calculates, collects, and remits. Sales you make through your own website or by direct invoice remain yours.
Is What You’re Selling Actually Taxable?
Nexus only tells you the state can require you to collect. What you owe on any given invoice still depends on whether the item is taxable there.
Tangible goods are taxable in the vast majority of states. The usual exceptions are necessities: many states exempt groceries, prescription medications, and sometimes clothing.
Services are more selective. Only four states — Hawaii, South Dakota, New Mexico, and West Virginia — tax services by default. Elsewhere, a service is taxable only if the state specifically lists it. An accounting firm in most states will not add sales tax; a landscaping company or an IT repair shop might, depending on the state.
Software-as-a-service and digital downloads are the least predictable category. Roughly half the states tax SaaS, and the rest treat it as an exempt service. Some states split the treatment based on whether the buyer is a business or a consumer. If you sell digital products, check each state where you have nexus individually.
Which Rate Applies
Once you know the sale is taxable, the rate depends on sourcing rules and on how much local tax stacks on top of the state rate.
Origin Versus Destination
About a dozen states use origin-based sourcing, meaning you charge the rate for your own business location. Texas, Pennsylvania, Ohio, and Missouri are in this group. Most states use destination-based sourcing, where the rate is set by the buyer’s shipping address or the location of service delivery. Ship products to customers across multiple destination-based states and you can end up managing dozens of rates.
State Plus Local
The rate on your invoice is rarely the state rate alone. Most states let counties and cities add their own taxes. State rates run from 2.9% to 7.25%, but combined rates can reach 11% or higher in parts of Louisiana.1Tax Foundation. State and Local Sales Tax Rates, 2026 The gap between the state rate and the true combined rate is typically 2 to 4 percentage points, which is enough to create real exposure if you only charge the state portion.
To find the combined rate for a specific address, use your state’s tax authority website or an automated rate lookup that maps addresses to tax districts. Zip codes alone are unreliable, because one zip code can span multiple tax jurisdictions.
Applying the Rate to the Invoice
The arithmetic is simple; the trick is knowing what dollar figure the rate applies to.
Start with the taxable subtotal. Add up only the taxable line items. If your invoice mixes taxable office supplies with exempt groceries, keep them separate and run the calculation on the taxable portion.
Adjust for discounts. Trade discounts, volume discounts, and store-issued coupons generally reduce the amount subject to tax. Sell an item for $200 with a $30 store discount and you calculate tax on $170. Manufacturer coupons work differently, because the manufacturer reimburses the seller, so the full pre-coupon price typically remains the taxable amount. Early-payment discounts, such as 2% off if paid within ten days, also generally don’t reduce the taxable receipt.
Handle shipping carefully. Whether shipping is taxable depends on the state. In many jurisdictions, if the product shipped is taxable, the shipping charge is taxable too. If you combine shipping for taxable and nontaxable items into one line, some states will treat the entire shipping amount as taxable. Breaking shipping out by item can lower the tax and simplify your records.
A Worked Example
You invoice a customer for $1,500 of taxable goods, offer a $100 volume discount, and charge $75 shipping. The buyer’s jurisdiction taxes shipping on taxable goods, and the combined state and local rate is 8.25%.
- Taxable amount: $1,400 (goods after discount) + $75 (shipping) = $1,475
- Sales tax: $1,475 × 0.0825 = $121.69
- Invoice total: $1,475 + $121.69 = $1,596.69
Multiply the taxable amount by the combined rate, round to the nearest cent, add it to the invoice.
Showing the Tax on the Invoice
Format the tax as its own line. Show a clear subtotal of goods or services, then a separate line labeled “Sales Tax” that carries both the percentage rate and the dollar amount, then the final total. Most jurisdictions let you combine state and local into a single line, though some local rules differ. Writing the rate next to the figure, for example “Sales Tax (8.25%): $121.69,” gives the buyer transparency and makes reconciliation at filing time easier.
Include your sales tax permit number or tax identification number on the invoice. Tax authorities expect it in your documentation if they audit, and many states require it on tax-related documents.
When You Add Nothing, Even in a Taxable State
Some invoices in a taxable jurisdiction still carry no tax. Wholesale is the common case. If your buyer is purchasing to resell rather than consume, they give you a resale certificate and you invoice without tax; the tax gets collected downstream when the item reaches the end consumer.
Keep the certificate on file and be able to tie it to the transaction. If an auditor asks why you didn’t collect, a verbal claim isn’t enough. A valid certificate should include the buyer’s name and address, their tax registration number, a description of what they’re purchasing, and a signature declaring the purchase is for resale under penalty of perjury.
Government agencies and certain nonprofits are also exempt, with the same documentation rule. Get the certificate before the sale and verify the registration number. Accepting a certificate you know to be fraudulent can make you liable for the uncollected tax plus penalties.
Why the Number Has to Be Right
If you fail to collect tax you should have, the state can assess you for the full amount you should have collected, even though you never received that money from your customer. Going back to buyers months or years later to ask for tax on old purchases is not a realistic option, so the liability comes straight out of your margin. Late filing penalties commonly start at 5% to 10% of the unpaid tax for the first month, with interest accruing on top. An audit that turns up a wrong rate applied across two years of invoices can produce a back-tax bill that dwarfs the effort it would have taken to look up the rate correctly the first time.