If you run a small business, sales tax is a collection job you do on behalf of the government: you charge it to customers in every state where your business has a sufficient connection, then send it to that state on the schedule your permit assigns. Five states have no statewide sales tax at all (Alaska, Delaware, Montana, New Hampshire, and Oregon). The other 45 states and Washington, D.C. each set their own rates, exemptions, thresholds, and filing rules, so a business selling in more than one place is really complying with more than one system at once. The money you collect never belongs to your business; it’s held in trust and must be remitted. Getting it wrong quietly accumulates back taxes, penalties, and interest that can sit unnoticed for years.
When You Have to Start Collecting: Nexus
Your obligation to collect in a given state begins when you establish nexus there. Nexus comes in two forms, and either one is enough on its own.
Physical nexus is the older idea. It exists when your business has a tangible footprint in the state: a storefront, warehouse, office, or employees working in the area. Storing inventory in a third-party fulfillment center counts in most states. If you ship through Amazon FBA, your inventory may sit in warehouses across a dozen states you’ve never set foot in, and each one can create a collection obligation.
Economic nexus does not require any physical presence. In 2018, the Supreme Court held in South Dakota v. Wayfair, Inc. that states can require out-of-state sellers to collect sales tax based purely on the volume of sales into the state. South Dakota’s threshold, which the Court treated as a model, was $100,000 in annual sales or 200 separate transactions delivered into the state.1Supreme Court of the United States. South Dakota v. Wayfair, Inc., et al. Nearly every state with a sales tax has adopted an economic nexus rule since, and $100,000 has become the standard dollar threshold. At least 15 states have dropped the 200-transaction test and kept only the dollar figure.
One detail that catches sellers by surprise: most states measure the $100,000 against gross sales, not just taxable sales. Exempt sales and even sales of nontaxable services can count toward the threshold. Once you cross the line in a state, you generally have 30 to 60 days to register and start collecting.
Which Rate to Charge
Once you know where you have to collect, the next question is how much. About a dozen states use origin-based sourcing, meaning you charge the tax rate where your business is located. The other 38 states and Washington, D.C. use destination-based sourcing, meaning you charge the rate where your customer receives the product.
There is one simplification. When you sell into a state as a remote seller (economic nexus, no physical location there), the sale is almost always destination-sourced regardless of the state’s general rule. Origin sourcing typically only applies to sales inside the state where you’re physically located. For most cross-border online sales, that effectively means destination sourcing.
The combined rate at any given address can stack state, county, city, and special district taxes on top of each other. State-level rates run from zero to 7.25%, but once local taxes are layered on, the combined rate at a customer’s address can exceed 10% in some areas. For anyone selling into multiple jurisdictions, sales tax software that plugs into checkout is close to a necessity.
Sales Through Marketplaces
If you sell on Amazon, Etsy, eBay, or Walmart Marketplace, the platform is probably already collecting and remitting sales tax on your behalf. Nearly every state with a sales tax has enacted a marketplace facilitator law that shifts the collection duty from individual sellers to the platform.2Streamlined Sales Tax Governing Board, Inc. Marketplace Facilitator
That doesn’t always eliminate your own filing obligations. Some states still require marketplace sellers to register and file returns even when the platform handles collection.2Streamlined Sales Tax Governing Board, Inc. Marketplace Facilitator And if you sell through both a marketplace and your own website, you still have to collect tax yourself on the direct sales. The marketplace only covers transactions that flow through its platform.
Services and Digital Products
Most people think of sales tax as a tax on physical goods. That is roughly the starting point, but not the whole picture. Four states tax services by default and exempt only what statutes carve out. The other 41 states with a sales tax exempt services by default and tax specific categories they’ve chosen to list. Commonly taxed categories include repair and maintenance work on tangible property, real property services like landscaping and janitorial work, some personal services, and admission to amusement and recreation venues. Professional services such as legal, accounting, and medical care remain the least taxed. If your business sells services, you have to check your state’s taxable service list.
Digital products add another layer. Most state sales tax codes were written before digital commerce, and states have taken different approaches to downloads, streaming, and software subscriptions. Some apply a “tangible form” test: if the physical version would be taxable, the digital version is too. The 24 states in the Streamlined Sales and Use Tax Agreement use standardized definitions for digital audio, audiovisual works, and digital books, but each state still decides independently whether to tax or exempt them.3Streamlined Sales Tax Governing Board, Inc. Streamlined Sales Tax If you sell software, e-books, online courses, or digital media, the answer to “is this taxable” can flip depending on the customer’s state.
Registering for a Sales Tax Permit
You need a permit in a state before you start collecting tax there. Collecting without one is illegal in most states, and selling without collecting when you have nexus builds up back-tax liability. Registration is free in most states; a handful charge a small fee, typically under $25.
The application generally asks for your legal business name, primary address, federal employer identification number, and business structure (LLC, S-Corp, C-Corp, sole proprietorship). Sole proprietors without employees can usually use a Social Security number in place of an EIN. You’ll also give an industry classification code and an estimate of expected taxable sales, which the state uses to set your filing frequency.
If you need to register in many states at once, the Streamlined Sales Tax Registration System lets you file a single application covering all 24 member states.3Streamlined Sales Tax Governing Board, Inc. Streamlined Sales Tax For non-member states, you have to register individually through each state’s department of revenue. Most applications process within a few business days.
One easy thing to miss: a change in ownership or business structure typically voids your existing permit and requires a new registration. Converting a sole proprietorship to an LLC, adding a partner, or selling the business all qualify. Operating under an expired or invalid permit creates the same liability as never having registered.
Filing, Remitting, and Late Penalties
Once you’re registered, the state assigns a filing frequency based on your expected volume. High-volume sellers file monthly, mid-range sellers file quarterly, and low-volume sellers file annually. The state can change your frequency if your sales rise or fall. Filing usually means logging into the state’s online portal, entering your total sales, taxable sales, exempt sales, and tax collected, and submitting payment.
Most states require electronic payment through ACH bank transfer once your tax liability crosses a certain monthly amount. Some accept credit card payments through their portals, but those often carry processing fees in the 2% to 3% range. ACH is free in nearly every state and clears within one to two business days. Save the confirmation number the system generates; that is your proof of timely filing if a question comes up later.
Late Filing Penalties
Missing a deadline triggers penalties that vary by state but follow a common pattern. The typical structure is a percentage of the unpaid tax, often starting at 5% to 10% for the first month, that increases the longer you wait and usually caps between 25% and 35% of the total tax due. Many states also impose a minimum floor around $50, so even a return with zero tax due can generate a penalty if it’s filed late. Interest accrues on top of the penalty from the original due date. For businesses that fail to file at all, or that are found to have intentionally avoided collection, some states impose penalties that can reach double the tax owed.
Timely Filing Discounts
Roughly half the states offer a vendor discount for filing and paying on time. The discount is typically a small percentage of the tax you collected, from about 0.5% to 5%, often with a monthly or annual cap. It’s usually applied automatically when you file on time, though some states require electronic filing to qualify. For a business remitting several thousand dollars in sales tax a month, even a 1% to 2% discount adds up over a year.
Exemptions and Resale Certificates
Not every sale is taxable. The most common exemption applies when your buyer is purchasing goods for resale rather than personal consumption. The buyer provides a resale certificate, you keep it on file, and you don’t charge tax. The tax gets collected once, at the final sale to the end consumer.
The same principle works the other way. When you buy inventory from a wholesaler or manufacturer to resell, you give them your resale certificate to avoid paying tax at that stage. Other common exemptions cover sales to nonprofits and government agencies, and in many states certain goods like groceries, prescription medications, and clothing. Each state maintains its own list, and the differences can be granular.
Keeping Exemption Certificates in Order
This is where most small businesses get tripped up in an audit. If you made a tax-free sale and can’t produce the corresponding exemption certificate, you owe the tax yourself, plus interest. It does not matter whether the buyer was legitimately exempt. No paperwork, no exemption. Keep digital copies of every certificate organized by customer name, and check for expirations. Best practice is to retain these records permanently, or at minimum for the length of your state’s audit lookback period, typically three to four years, though some states can look back further.
Drop Shipping
Drop shipping creates a three-party transaction that complicates the normal certificate flow. The tax that applies is the rate in the state where the customer receives the goods, and about 10 states will only accept their own state-specific resale certificate with a local registration number rather than a home-state or multistate form. If you drop ship, confirm what documentation each destination state requires before the first shipment goes out.
Use Tax: The Obligation Sellers Overlook
Use tax is the mirror image of sales tax. When your business buys something and the seller doesn’t charge sales tax, you generally owe use tax to your own state at the same rate. This comes up constantly: supplies bought from an out-of-state vendor not registered in your state, equipment ordered online from a seller who doesn’t collect, or items bought using your resale certificate but then used in your own business instead of resold.
The obligation to self-assess and remit falls entirely on the buyer. No one sends you a bill. You report it on your regular sales tax return (most states include a use tax line) and pay it alongside the tax you collected from customers. The most dangerous version of this is using a resale certificate to buy items tax-free and then consuming them yourself. States treat that as an abuse of the certificate. You’ll owe the tax you avoided plus a penalty that can reach 50% of the unpaid amount in some states, even without any intent to defraud.
Audits and Multi-State Compliance
Sales tax audits are not random the way people assume. Auditors prioritize businesses in high-risk industries, companies that recently changed ownership, sellers whose reported sales look inconsistent with industry peers, and businesses flagged by an audit of one of their vendors or customers. New businesses also get selected as routine compliance checks.
The examiner compares your total revenue, often pulled from your federal income tax return, against the taxable sales you reported. They look at whether the gap between gross sales and taxable sales is explained by documented exemptions. They review your purchase records for items you should have paid sales or use tax on. Most audit assessments come down to missing paperwork rather than intentional evasion. The single best defense is clean records: organized exemption certificates, sales tax returns reconciled to your accounting records each period, and reported gross sales that match your income tax return.
Selling into multiple states is where sales tax compliance turns from manageable into a full job. Each state runs its own rates, rules, exemptions, deadlines, and return formats. The Streamlined Sales and Use Tax Agreement helps by standardizing definitions and offering centralized registration across its 24 member states, but that still leaves more than 20 states outside the system.3Streamlined Sales Tax Governing Board, Inc. Streamlined Sales Tax The Wayfair decision itself noted that member states provide sellers access to free sales tax software and immunity from audit liability when they use it.1Supreme Court of the United States. South Dakota v. Wayfair, Inc., et al.
For businesses that have outgrown spreadsheets, automated sales tax platforms integrate with most e-commerce and point-of-sale systems to calculate the right rate at checkout, track where you have nexus, and file returns for you. Pricing runs from around $20 a month for small sellers up to several hundred for higher volumes. That is almost always cheaper than the penalty for getting a rate wrong in a jurisdiction you didn’t realize you had to file in, or the cost of manually filing returns in 15 states every quarter.