Last updated September 9, 2026
Sales tax becomes a real operating problem long before most online businesses expect it. At Cloud Water Filters, we went from filing in one state to managing obligations across many states as sales grew. What started as a small monthly task became a recurring mix of registrations, returns, payment deadlines, notices, and data cleanup.
The rule changed in 2018. In South Dakota v Wayfair, the Supreme Court let states require remote sellers to collect sales tax even without a physical location in the state. A seller can now create sales tax nexus through its sales alone.
The practical answer is simple. Track sales by state, learn what creates nexus, register before collecting, charge the right tax, file every required return, and keep the money ready to remit. You can handle a small footprint yourself. Once you reach several states, a full-service tool such as Numeral or Zamp can save far more time than it costs.
What Sales Tax Is
Sales tax is a state or local tax on a taxable sale. The seller usually collects it from the customer and sends it to the government.
That money is not revenue. Your accounting system should record collected sales tax as a liability until you remit it. If you fail to collect tax that was due, the state may still demand the money from your business. That turns the customer’s tax into your expense.
Five states do not impose a statewide sales tax: Alaska, Delaware, Montana, New Hampshire, and Oregon. Alaska still allows local sales taxes, and some Alaska localities apply remote-seller rules. Everywhere else, state and local rules can overlap.
Sales Tax Nexus Is the Trigger
Sales tax nexus is the legal connection that lets a state require your business to register, collect tax, and file returns. Nexus can come from physical activity or economic activity.
Physical Nexus
Physical nexus can arise from an office, store, warehouse, employee, contractor, inventory, or other in-state activity. The exact rule varies by state.
Inventory is the trap for many online sellers. Goods stored in a third-party warehouse may create physical nexus even if you do not own the building. Remote employees can also create state tax exposure. Do not assume your company has no physical presence because it has no office there.
Economic Nexus
Economic nexus can arise when sales into a state cross that state’s threshold. Many states use $100,000 in sales, but the rules are not uniform. Some use a higher amount. Some count gross sales, while others count retail or taxable sales. Several states have removed transaction-count tests that once applied. The Streamlined Sales Tax state guidance links to each state’s current rule.
The measurement period also changes by state. A state may look at the current calendar year, the prior year, or a rolling 12-month period. Some require collection as soon as you cross the threshold. Others give you time to register.
Run a sales-by-state report every month. Waiting until year-end can leave you collecting too late and paying old tax from company cash.
The Two Questions People Mix Up
Nexus and taxability are separate questions. Nexus tells you where you may have a duty. Taxability tells you which sales are taxed.
A business can cross a state’s nexus threshold even when some or all of its products are exempt. Some states count exempt or wholesale sales toward the threshold. You may still need to register, collect exemption certificates, and file returns showing little or no tax due.
This distinction matters because a dashboard that flags $100,000 of sales does not finish the analysis. You still need to know which sales the state counts and whether the products sold there are taxable.
What Products and Services Are Taxable
Most states tax many physical products, but exemptions and reduced rates can apply to food, clothing, medicine, manufacturing inputs, and other categories. Digital goods, software, subscriptions, and services are less consistent.
A software subscription may be taxable in one state and exempt in another. Installation, warranties, shipping, and bundled services can change the result. A product name in your checkout system is not enough. Your tax engine needs a category that matches what you actually sell.
B2B sales create another layer. A customer that buys for resale may give you a resale certificate. A nonprofit or government buyer may provide another exemption document. Keep valid certificates with the sale. An unchecked exemption box is not audit support.
How Online Sales Tax Works
Online sales tax compliance follows the same six-step loop in every state, even though the details change.
1. Track sales by customer location and sales channel.
2. Measure physical and economic nexus in each state.
3. Confirm whether your products or services are taxable.
4. Register for a sales tax permit before you begin collecting.
5. Calculate and collect the right rate at checkout or on the invoice.
6. File the return and remit the money by the state’s deadline.
A sales tax permit is separate from your federal employer identification number. If you still need the federal number, DailyDime has a step-by-step guide to getting an EIN from the IRS.
Most states assign monthly, quarterly, or annual filing schedules based on sales volume. A registered business may need to file a zero return even when it collected no tax. Missing that empty return can still create a penalty.
Marketplace Sales Do Not Solve Everything
Marketplace facilitator laws usually make platforms such as Amazon collect and remit tax on sales made through their marketplaces. The protection stops at the edge of that marketplace.
If you also sell through your own website, those direct sales remain your responsibility. Marketplace sales may also count toward a state’s economic nexus threshold. California’s marketplace tax guide, for example, tells sellers to include marketplace and direct sales when measuring its threshold.
Keep marketplace reports even when the platform remits the tax. A state may ask you to prove which sales the marketplace handled. If you use Amazon FBA, also review where your inventory sits because stored inventory may create physical nexus.
Sales Tax Software Does More Than Calculate a Rate
A checkout tax feature can calculate tax without handling the rest of compliance. Before you buy a tool, list the jobs you want it to own.
A full-service provider may also monitor nexus, register states, classify products, file returns, remit tax, manage exemption certificates, and answer notices. Compare the full workflow. Cheap calculations are not cheap if your team still handles everything else.
Why Numeral Deserves a Close Look
Numeral is now a serious full-service sales tax option for online businesses. It combines nexus monitoring, registrations, filings, remittance, exemption certificates, tax notices, and calculation in one service.
Numeral raised a $35 million Series B in September 2025 at a reported $350 million valuation. The round came six months after an $18 million Series A. At the time, TechCrunch reported that Numeral had grown revenue 3.5 times in one year and served more than 2,000 software and ecommerce customers.
The company now says it has more than 3,000 customers and $57 million in total funding. Funding does not prove that a tax return will be correct. It does give Numeral more resources to build the product, hire tax experts, and expand its coverage.
For managed U.S. compliance, Numeral’s published pricing was $150 per state registration and $75 per filed return when checked on September 9, 2026. Standard accounts have no setup fee or required annual contract. Free nexus monitoring lets a business connect its sales channels, run a nexus study, and receive threshold alerts.
The per-return price is easy to understand, but calculate the annual total. Ten states filing monthly would cost $9,000 per year for returns before new registrations or added services. Quarterly and annual states cost less. Your filing schedule matters more than your state count.
Numeral also says it offers more than 30 integrations, coverage in more than 70 countries, AI product classification, government portal monitoring, and a virtual mailbox for tax notices. It guarantees on-time filing or payment of resulting penalties and interest. Read the guarantee terms before relying on it.
Numeral belongs on the shortlist for ecommerce, software, wholesale, and international sellers. Its clear U.S. pricing makes comparison easier. The real test is whether its integrations, service team, and filing process fit your business.
Numeral Compared With Other Sales Tax Tools
The right sales tax tool depends on how much work you want to keep, what you sell, and where you sell it.
Zamp
Zamp is the service we use for U.S. sales tax at Cloud Water Filters. I switched after Avalara’s full-service process still left too much registration work with me. Zamp connected our Stripe and TrueMed payment flows, and its support team has been responsive when we added states or worked through API issues.
That is a recommendation based on use, not a feature-page review. If I were choosing today, I would quote both Zamp and Numeral. Zamp has earned my trust in our account. Numeral now has enough scale, funding, and product breadth to deserve a direct comparison.
Avalara
Avalara remains a serious option for large or complex businesses. It supports detailed product tax rules, exemption certificate workflows, international taxes, and a large integration network. That depth can help an enterprise with many systems and product types. A smaller company may find the setup, contracts, and service model heavier than it needs.
Shopify Tax and Stripe Tax
Shopify Tax and Stripe Tax make sense when most sales already run through the same platform. They can monitor obligations and calculate tax inside the checkout flow. Confirm which registrations, returns, remittances, and notices the product handles itself and which work goes to a partner. Calculation is only one piece of compliance.
Anrok and Kintsugi
Anrok focuses on software and digital products. Kintsugi serves growing companies that want automated sales tax compliance. Review either one when its integrations match your business, but three serious quotes will teach you more than eight generic demos.
When to Stop Handling Sales Tax Yourself
Manual filing can work with one state, one sales channel, and a simple product. Automate when you approach nexus in several states, sell through several channels, manage exemptions, or lose days to filings and notices.
Our breaking point was not transaction volume alone. It was the number of state accounts and the amount of follow-up. Once sales tax consumes time that should go to finance, operations, or growth, the software has a clear return.
What to Do If You Are Behind
Do not begin by registering in every state. First measure the exposure. Registration can alert a state to prior periods and may limit your ability to use a voluntary disclosure program.
1. Export sales for at least the periods covered by each state’s threshold rules.
2. Group sales by state, sales channel, product type, and taxable status.
3. Map physical nexus from employees, contractors, offices, and inventory.
4. Identify the first date each state threshold was crossed.
5. Estimate tax, penalties, interest, and unfiled returns.
6. Ask a sales tax adviser whether a voluntary disclosure agreement makes sense before contacting the state.
A voluntary disclosure agreement may reduce penalties and limit the number of prior years a state reviews. It is not automatic, and the rules vary. This is one of the few parts of sales tax cleanup where professional advice can save money before you take the first public step.
Sales Tax Nexus Can Lead to Other State Taxes
Sales tax nexus does not automatically create state income tax nexus, but the same activity can create both. Employees, inventory, in-state services, and high sales can trigger separate filing duties.
Federal Public Law 86-272 may protect some sellers of physical goods from state net income tax when their in-state activity stays within narrow limits. It does not provide broad protection for services, software, or every state tax. Ask your tax adviser to review income, franchise, and gross-receipts taxes when you add sales tax registrations.
A Practical Sales Tax Checklist
Start with the report, not the software demo.
- Export sales by destination state each month.
- Track physical presence and inventory locations.
- Review state thresholds before you cross them.
- Register before collecting tax.
- Map each product to the right tax category.
- Collect and store exemption certificates.
- Reconcile collected tax to filed returns and cash paid.
- Keep marketplace reports and proof of facilitator collection.
- Assign one person or provider to own notices and deadlines.
Then compare Numeral, Zamp, or another provider using your real filing count and sales channels. A polished demo is nice. A clean return filed on time is the product.
The Bottom Line
Sales tax is manageable when you separate the job into nexus, taxability, registration, calculation, filing, and remittance. The trouble starts when a business assumes its checkout platform handles all six.
Numeral has grown into a credible full-service option, backed by $57 million in funding, transparent U.S. pricing, more than 3,000 customers, and a broad compliance product. Zamp remains the service I can recommend from direct experience. Put both on the shortlist if your online business has outgrown manual filings.
The first move costs nothing. Pull last year’s sales by state and find out where you stand before a state does it for you.