# US Sales Tax Importers Online Sellers: Nexus, Registration, and Compliance

US sales tax importers online sellers face is a state-by-state obligation triggered by nexus: a connection between your business and a state, created by storing inventory there, hitting sales thresholds, or having people on the ground. This guide explains how nexus works for importers, when marketplaces handle collection for you, and how to stay compliant without drowning in fifty rulebooks.

For importers selling online in the United States, sales tax is the compliance topic most likely to be discovered late and expensively. The business imports goods, sells them on Amazon or a Shopify store, revenue grows, and nobody thinks about sales tax until a state notice arrives or an accountant asks where inventory is stored. US sales tax importers online sellers deal with is genuinely confusing because there is no single national system: each state sets its own rules, its own thresholds, and its own filing rhythms. But the underlying logic is learnable, and most of the pain comes from not knowing the logic exists. That learnability is good news for US sales tax importers online sellers: the system is complex, not mysterious. This guide gives you the mental model and the practical steps.

What is nexus and why does it decide everything?

Nexus is the legal connection between your business and a state that gives the state the right to require you to collect its sales tax. No nexus in a state, no collection obligation there. Nexus in a state, and you generally must register, collect the right tax on taxable sales, and file returns. Every question in US sales tax importers online sellers compliance reduces to two steps: where do I have nexus, and what do I owe in each of those states.

Nexus comes in two main flavors. Physical presence nexus is the older kind: your business has people, property, or inventory in the state. For importers, the classic trigger is inventory. Goods sitting in your own US warehouse, a 3PL facility, or an Amazon fulfillment center in a state generally create physical nexus there. Amazon's fulfillment network moves inventory between states to optimize delivery, which means FBA sellers can develop nexus in many states without ever choosing to. Employees or contractors working in a state, attending trade shows with order-taking, or owning or leasing property there can also create it. If your goods physically sit in a state, assume nexus until a professional tells you otherwise. That assumption-first posture is the safest default in US sales tax importers online sellers planning.

Economic nexus is the newer kind, created by the volume of your sales into a state rather than your physical footprint. Following the Supreme Court's Wayfair decision, states can require collection from sellers with no physical presence once their sales into the state cross set thresholds, typically framed as a dollar amount of sales, a number of transactions, or both. The thresholds differ by state and change over time, so verify the current figures against official state sources rather than relying on any article's numbers. For an importer selling nationally online, economic nexus is what turns a business with inventory in three states into a business with obligations in twenty. This multiplier effect is why US sales tax importers online sellers footprints grow faster than founders expect.

The practical upshot: map both kinds. List every state where your inventory sits or has sat, including FBA movements, and track your sales by state against each state's economic thresholds. That map is your compliance footprint, and it changes as the business grows, so revisit it at least annually. Keeping that map current is the core administrative habit of US sales tax importers online sellers compliance.

Do marketplaces collect sales tax for you?

This is the question that confuses US sales tax importers online sellers most, because the answer is a qualified yes that lulls people into a false sense of completeness. Most states now have marketplace facilitator laws requiring large platforms like Amazon, eBay, Walmart, and Etsy to collect and remit sales tax on third-party sales made through their marketplaces. If you sell only through Amazon, Amazon handles the collection and remittance in the states where these laws apply, which is most of them. Many sellers hear this and conclude they have no sales tax obligations at all, which is the most common US sales tax importers online sellers misconception. That conclusion is usually wrong in at least one direction.

First, marketplace collection covers the marketplace sales, not your other channels. If you also sell through your own Shopify store, your own website, or wholesale to retailers, those sales are your collection responsibility in every state where you have nexus. The marketplace does not cover them. Second, collection is not the same as registration and filing. Some states still expect sellers to register or file returns even where the marketplace collected the tax, particularly to report the marketplace-facilitated sales as exempt or to maintain the registration tied to inventory nexus. The rules here are state-specific and genuinely fiddly, which is why US sales tax importers online sellers guidance always ends with "check each state."

Third, the marketplace's collection does not remove your nexus; it just changes what you must do about it. You still have the connection to the state through your inventory or sales volume. In practice this means keeping registrations current, understanding each state's filing expectations for marketplace sellers, and not assuming that Amazon's compliance is your compliance. Treat marketplace facilitator laws as a major simplification of collection, not as an exemption from the system. Internalizing that distinction is half the battle in US sales tax importers online sellers compliance.

How do you register and file in each state?

US sales tax importers online sellers registration happens state by state, through each state's department of revenue or equivalent agency. There is no federal registration and no single application. The typical process: create an account on the state's tax portal, provide your business details and EIN, describe your business activity, and receive a sales tax permit or license. Some states issue the permit quickly online; others take weeks. A few states charge a registration fee or require a security deposit, particularly for out-of-state sellers. None of this is difficult in isolation; the difficulty is entirely in the multiplication across states. That multiplication is the defining administrative feature of US sales tax importers online sellers life.

Once registered, you file returns on the schedule the state assigns, usually monthly, quarterly, or annually based on your tax liability there. The return reports your taxable sales in the state, the tax collected, and any deductions such as marketplace-facilitated sales that the platform already handled. Filing is due even in periods with no tax to remit in many states: a zero return is still a return, and missing it draws penalties. Calendar every filing deadline when you register, because the penalties for late filing are automatic and unsympathetic, and they compound across states fast. A shared compliance calendar is one of the highest-value tools in US sales tax importers online sellers operations.

Record-keeping underpins all of it. Keep sales records by state, marketplace collection reports, exemption certificates from wholesale customers, and import documentation organized and accessible. States can audit back several years, and an audit without records goes badly. Audit readiness is the unglamorous backbone of US sales tax importers online sellers compliance. If you sell both retail and wholesale, resale certificates from your B2B customers are what keep you from owing tax on those sales; collect them before the sale, not during the audit. This paperwork discipline is unglamorous and it is the difference between a routine filing life and a painful one.

US sales tax importers online sellers: what trips importers up specifically?

Importers face a few wrinkles that domestic sellers do not, and they sit at the intersection of US sales tax importers online sellers rules and the import process itself. The first is the inventory question at the moment goods land. Your shipment clears customs and goes to a US warehouse or an Amazon inbound center. From that moment, you likely have physical nexus in that state, which means the registration clock arguably starts then, not when sales begin. Businesses that register only after sales pick up can have a gap period of unregistered nexus. The clean approach is to register in warehouse states as part of your launch checklist for that location. Make it a line item, not a judgment call: US sales tax importers online sellers checklists should treat warehouse-state registration as automatic.

The second is the importer-of-record and resale structure. If you import goods and sell them wholesale to US distributors, those sales are generally for resale and not subject to sales tax collection by you, provided you hold valid resale certificates. But the inventory sitting in the state still creates nexus, and the registration and filing obligations tied to that nexus do not vanish because your sales are wholesale. Nexus and taxability are separate questions: nexus decides whether you are in the system, taxability decides whether a given sale gets taxed. Keeping those two questions separate is a hallmark of mature US sales tax importers online sellers compliance.

The third is the multi-state creep of a growing online business. You start with inventory in two states and economic nexus in five more, and two years later the footprint is twenty states and nobody did a fresh nexus review. Build the review into your annual routine: pull sales by state, list inventory locations including FBA movements, check thresholds, and register where newly required. Voluntary registration when you discover a new obligation beats a state notice every time, in penalties, in interest, and in sleep quality. That asymmetry makes proactive review the cheapest insurance in US sales tax importers online sellers practice.

The fourth is assuming the accountant has it covered without ever discussing it. Many small-business accountants focus on income tax and payroll; sales tax across twenty states is a specialty. If your advisor has not asked about your inventory locations and sales-by-state data, they are probably not managing this for you. Either brief them explicitly or engage a sales tax specialist. The cost of advice here is small compared to the cost of multi-state back liability, a tradeoff every US sales tax importers online sellers business should weigh early.

Key takeaways

  • US sales tax importers online sellers obligations are decided by nexus: physical presence from inventory, people, or property, and economic nexus from sales volume into each state.
  • Inventory in a state generally creates nexus there, including stock in 3PL warehouses and Amazon fulfillment centers, which can multiply across many states.
  • Marketplace facilitator laws mean platforms collect on marketplace sales in most states, but they do not cover your direct or wholesale channels and do not erase nexus.
  • Register state by state, file on each state's schedule even for zero-tax periods, and calendar every deadline at registration time.
  • US sales tax importers online sellers should register in warehouse states as part of the location launch, keep resale certificates for wholesale sales, and run a fresh nexus review annually.
  • Confirm thresholds, rates, and filing rules against official state sources; they change, and articles go stale.

Frequently asked questions

### Do I need to collect sales tax if I only sell on Amazon?

Amazon collects and remits sales tax on your Amazon sales in most states under marketplace facilitator laws, so the collection burden there is largely handled. But you may still need to register in states where your inventory creates nexus, and some states expect returns or registrations from marketplace sellers regardless. If Amazon is your only channel, your obligations are much lighter than a multichannel seller's, but "lighter" is not "zero." Confirm each inventory state's expectations rather than assuming the marketplace covers everything.

### What is economic nexus and how do I know if I have it?

Economic nexus is the obligation to collect a state's sales tax based on your sales volume into that state, even with no physical presence there. Each state sets its own thresholds, usually a dollar figure, a transaction count, or both, and they change over time. You determine it by tracking your sales into each state and comparing against that state's current thresholds, which you should verify on the state's official revenue site. Sales tax software can automate this tracking, and for sellers active in many states it is usually worth it. For US sales tax importers online sellers operating nationally, that automation typically pays for itself in avoided penalties alone.

### Do I owe sales tax in a state where I only have inventory but no sales?

Possibly yes on the registration side. Inventory in a state generally creates physical nexus, which typically requires registration and periodic filing, even if your taxable sales there are zero or handled by a marketplace. Many states require returns even for no-tax periods. The obligation to be in the system is separate from whether any particular sale is taxable, so do not confuse "no sales there" with "no obligations there."

### How do resale certificates work for importers selling wholesale?

When you sell to a US business that will resell your goods, that sale is generally exempt from sales tax collection if you hold a valid resale certificate from the buyer. You must obtain the certificate before or at the time of sale; chasing one during an audit is far less convincing. Requirements and accepted certificate forms vary by state, and some states want their own form rather than a multistate one. Keep certificates organized by customer and renew them as states require.

### What happens if I should have been collecting but was not?

You face back registration, uncollected tax liability, penalties, and interest, with specifics varying by state. Voluntary disclosure programs in many states let businesses come forward with reduced penalties compared to being caught, so discovering a gap is a reason to act quickly, not to hide. Talk to a sales tax professional about voluntary disclosure in the affected states rather than quietly starting to collect and hoping the past goes unnoticed.

Conclusion

US sales tax importers online sellers compliance comes down to a discipline, not a trick: know where you have nexus, register there, collect where the sale is taxable, file on time, and review the footprint every year. Marketplace facilitator laws removed the hardest part of collection for platform sales, but they left the rest of the system intact: your direct channels, your wholesale paperwork, your registrations, and your filing calendar. Importers have one extra reason to be systematic, because inventory landing in a new state starts the nexus clock before the first sale. That early trigger is the signature US sales tax importers online sellers wrinkle, and the reason warehouse launches need a tax checklist. Build the nexus review into your annual routine alongside the financial review, keep the records that audits ask for, and get professional help for the states that get complicated. Sales tax will never be anyone's favorite subject, but handled as a routine it stays a routine instead of becoming a crisis.