To calculate and file sales tax for your business, you work through four steps in order: identify every state where you have an obligation to collect, apply the correct combined rate to each taxable sale, subtract exempt sales to arrive at net taxable sales, and file the return your state provides with payment by the deadline. Forty-five states impose a state-level sales tax, and 38 of those add local taxes on top through counties, cities, or special districts.1Tax Foundation. State and Local Sales Tax Rates, 2024 The math is not difficult, but the money you fail to collect comes out of your own pocket, so each piece has to be right.
Where You Owe: Nexus
Your obligation to collect in a given state depends on whether you have nexus there. Nexus is the legal connection that gives a state the authority to require you to act as its tax collector, and it comes in two forms.
Physical nexus exists when your business has a tangible footprint in the state. An office, warehouse, or retail store creates it, and so do less obvious things: an employee working remotely from the state, inventory sitting in a third-party fulfillment center, or selling products at a trade show or craft fair.
Economic nexus is the newer standard. In 2018, the U.S. Supreme Court ruled in South Dakota v. Wayfair, Inc. that a state can require sales tax collection from businesses with no physical presence there as long as they have a sufficient economic connection.2Supreme Court of the United States. South Dakota v Wayfair, Inc., et al. (No. 17-494) The South Dakota law at issue set the threshold at $100,000 in annual sales or 200 separate transactions. Most states adopted similar thresholds, and a growing number have dropped the 200-transaction test, leaving $100,000 in gross sales as the sole trigger. If you ship across state lines, this is why you may owe tax in states you’ve never set foot in.
Register Before You Collect Anything
Once you know where you have nexus, get a sales tax permit from each of those states before you collect a single dollar. The permit goes by different names in different states (seller’s permit, sales tax license, retail license) but the function is the same. Most states let you apply online through the department of revenue, and the application asks for your federal employer identification number, business structure, physical address, and the type of goods or services you sell. Registration is free in most states; a handful charge a small fee or require a refundable security deposit.
Collecting sales tax without a valid permit is illegal in every state that imposes the tax, and you can be penalized for it even if you set aside the money to remit later.
Five states have no statewide sales tax: Alaska, Delaware, Montana, New Hampshire, and Oregon. Alaska is a special case because roughly 100 of its municipalities impose their own local sales taxes despite the absence of a state-level tax.
Finding the Right Rate for Each Sale
State-level rates currently range from 2.9% in Colorado to 7.25% in California, but the state rate is only the starting point.1Tax Foundation. State and Local Sales Tax Rates, 2024 Counties, cities, and special taxing districts each add their own layer. Special districts often fund infrastructure like transit systems and can tack on increments as small as an eighth of a percent.3FHWA – Center for Innovative Finance Support. Sales Tax Districts Combined rates reach 11% or higher in some localities.
The rate you charge depends on whether the state uses origin-based or destination-based sourcing. About a dozen states are origin-based, meaning the rate is set by where your business is located. The rest are destination-based, meaning the rate is set by where the buyer receives the product. Destination-based sourcing is more common and more burdensome, because you have to look up the exact rate for the customer’s shipping address rather than applying your own local rate to every sale.
Every state’s department of revenue publishes a rate lookup tool, usually searchable by zip code or street address. Use these tools rather than a static rate table you saved months ago. Local governments regularly vote on new tax measures that change rates mid-year, and under-collecting by even a fraction of a percent leaves you covering the difference.
Subtracting Exempt Sales
Not every sale is taxable. Exemptions fall into two broad categories: exempt products and exempt buyers.
On the product side, most states exempt unprepared groceries, and nearly all exempt prescription medications. Clothing exemptions are less uniform, with only a handful of states excluding everyday clothing from the tax base. Prepared food, candy, and soft drinks are usually taxable even where basic groceries are not. The specific list of exempt items varies by state; check the department of revenue for the categories that apply to what you sell.
On the buyer side, sales to tax-exempt organizations like nonprofits and government agencies are generally not taxable, and neither are sales to other businesses buying goods for resale. To protect yourself on these transactions, get a completed exemption or resale certificate from the buyer at the time of the sale. Thirty-six states accept the Multistate Tax Commission’s Uniform Sales and Use Tax Resale Certificate, which lets a single form cover purchases across multiple states.4MTC.gov. Uniform Sales and Use Tax Resale Certificate Multijurisdiction Keep the certificates on file permanently. In an audit they are your proof that you were right not to collect tax on the transaction. Without one, the auditor assesses the tax against you.
Doing the Calculation
Most states provide the return through a secure online portal where you log in with your registered business account. The form asks for your business name, tax identification number, the reporting period, and your sales figures. The calculation itself is a short sequence:
- Start with gross sales: total revenue from all sales during the period, before any deductions.
- Subtract exempt sales: sales to tax-exempt buyers, resale transactions, and out-of-state sales in states where you have no nexus.
- The result is net taxable sales. This is the number the tax rate applies to.
- Multiply net taxable sales by the applicable rate to get tax due. If you sell into multiple jurisdictions, the return includes a supplemental schedule where you break down taxable sales by city or county code and apply each local rate separately.
Then subtract any credits for tax previously collected on merchandise that was later returned, and add any use tax you owe on business purchases where no sales tax was collected. Most online systems perform the math automatically once you enter the figures. Even so, check that the total tax on the return matches what you actually collected. A gap between the two is exactly what triggers an audit inquiry.
Your return is only as defensible as the records behind it. Keep point-of-sale reports or invoices showing the date, amount, and location of every transaction, broken down by taxable and nontaxable sales. In destination-based states, tag each sale with the buyer’s delivery address so you can assign it to the correct local jurisdiction. Track shipping and labor charges separately, because their taxability varies by state. Most states require you to keep sales tax records for at least three years, some up to seven; keeping everything for seven years covers the longest audit windows and aligns with IRS record-keeping guidance for related federal deductions.5Internal Revenue Service. How Long Should I Keep Records
Filing Frequency and Deadlines
The state assigns your filing frequency when you register, and it will change over time as your collections change. The general pattern:
- Annual filing for businesses with minimal liability, often under a few hundred dollars per year.
- Quarterly filing for moderate volume, typically a few hundred to a few thousand dollars per year.
- Monthly filing above the state’s threshold, which can range from $600 per month in some states to over $30,000 per year in others.
The most common due date is the 20th of the month following the end of the reporting period. A monthly return for January is due February 20; a quarterly return covering January through March is due April 20. When the 20th falls on a weekend or holiday, the deadline typically moves to the next business day. Some states use different due dates; confirm yours when you register.
If your sales volume changes significantly, expect a reassignment. A jump in collections can bump you from quarterly to monthly filing, and missing the transition notice means filing late without realizing it.
Submitting and Paying
Nearly all states require electronic filing and payment. After reviewing the completed return in the portal, you submit and authorize payment in the same session. The standard payment method is an ACH debit from your business bank account. Some states accept credit cards, but they typically charge a convenience fee of 2% to 3% of the payment, which adds up fast on a large remittance.
Save the confirmation number and any receipt the portal generates. That confirmation is your proof of timely filing if a dispute comes up later. Store it with the underlying records for the period. A few states still accept paper returns for smaller filers, but several charge penalties for filing on paper when electronic filing is available. Set up your online account well before your first return is due so you’re not troubleshooting login problems on deadline day.
Don’t Forget Use Tax on Your Own Purchases
Use tax applies when you buy something taxable for your business and no sales tax was collected at the point of sale. The most common scenario is ordering supplies, equipment, or materials from an out-of-state vendor who doesn’t charge your state’s sales tax. The rate is identical to what you would have paid in sales tax. If the vendor charged another state’s tax, you usually get a credit for that amount and owe only the difference.
Report use tax on the same return you file for sales tax. There’s a line for it on most state forms, and some states let businesses with small use tax liabilities report and pay on their annual income tax return instead. Individual amounts can look trivial, but they accumulate, and auditors check for them routinely.
When a Marketplace Collects on Your Behalf
If you sell through a third-party platform like Amazon, Etsy, eBay, or Walmart Marketplace, you generally do not need to collect sales tax on those transactions yourself. Every state with a sales tax has enacted marketplace facilitator laws that shift the collection and remittance obligation to the platform for sales it facilitates.6Streamlined Sales Tax. Marketplace Facilitator State Guidance The platform calculates the tax, adds it to the buyer’s total, and sends it to the state.
This does not eliminate your filing responsibilities. You still file your own returns for sales made through your own website, at craft fairs, or through any other channel where the marketplace isn’t handling collection. And you still report marketplace-facilitated sales on the return in most states, even if the tax due on those transactions is zero. The state wants to see your full sales activity, not just the portion where you personally collected.
What Filing Late or Wrong Costs You
Late filing penalties commonly start at 5% to 10% of the tax due and can escalate to 25% or more the longer the return sits. Interest accrues on the unpaid balance from the original due date, and state interest rates for late tax payments run well above what you’d earn in a savings account.
The bigger risk is personal liability. Sales tax is legally a trust fund tax: you collect it from customers on behalf of the government, and the money is not yours. When a business fails to turn it over, most states hold the responsible individuals personally liable. Officers, directors, managers, and anyone with authority over the business’s finances can be on the hook for unpaid tax, penalties, and interest, even if the business is a corporation or LLC. States pursue these assessments aggressively because the money was never the business’s to spend.
Selling Into Multiple States
Multi-state sellers face the most complex version of this process because every state has its own rates, exemption rules, filing frequencies, and return formats. Twenty-four states have joined the Streamlined Sales and Use Tax Agreement, which standardizes definitions, filing procedures, and administration; registering through the Streamlined system signs you up for multiple member states at once.7Streamlined Sales Tax. Streamlined Sales Tax For states outside the agreement, you register and file individually.
Automated tax calculation software has become close to essential for businesses with economic nexus in more than a few states. These tools plug into your e-commerce platform, look up the correct rate for each transaction based on the shipping address, and generate the data each state’s return requires. The software costs money. So does the audit that finds you’ve been applying the wrong rate to transactions in a dozen states for three years.