Multistate tax is where small businesses are most likely to have an obligation they do not know about. The rules are set state by state, they are not uniform, and nothing notifies you when you cross a line. This article explains, at a high level, the connections that commonly create a filing requirement.

One caution before we start: there is no single national threshold. Any article that gives you one number for every state is oversimplifying. Each state sets its own rules, and they change.

Physical presence

The oldest and clearest connection is physical presence. An office, a storefront, a warehouse, owned or leased equipment, or inventory stored in a state can create an obligation there. Inventory is the one that catches online sellers off guard: goods stored in a third-party fulfillment warehouse may create a presence in that state even though the business never chose the location.

Employees working in another state

Employees generally create the strongest connection of all. When someone performs services in a state, the business is usually looking at payroll registration, wage withholding for that state, and state unemployment insurance in addition to any income or franchise tax question.

Remote workers

A single remote hire can change a company’s filing profile. If a business headquartered in one state hires a developer who works from home in another, the employer commonly needs to register for payroll in the employee’s state, withhold under that state’s rules, and evaluate whether the employee’s presence also creates an income tax filing obligation for the business.

Related traps include employees who relocate without telling the employer, and owners who work from a second home for part of the year.

Traveling and project-based work

Contractors, consultants, and service businesses that perform work on-site in other states can create obligations through that activity. Some states apply day-count or compensation thresholds for nonresident withholding; others look at whether the work itself constitutes doing business in the state. Construction and trades businesses are especially likely to encounter this.

Sales activity and economic nexus concepts

Following the U.S. Supreme Court decision in South Dakota v. Wayfair, states may require sellers without physical presence to collect and remit sales tax when the seller’s activity in the state exceeds a state-set threshold. This is commonly called economic nexus.

Thresholds are typically expressed as an amount of sales into the state, sometimes combined with a transaction count, measured over a defined period. The specific figures, the measurement period, and whether marketplace sales count toward the threshold all vary by state. Many states publish their current rules through their department of revenue, and the multistate resources maintained by the Streamlined Sales Tax Governing Board are a useful starting point for the states that participate.

Marketplace facilitator laws add another layer: when a platform collects tax on your behalf, your own registration duty may change, but those sales may still count toward a threshold in some states.

State registrations

Doing business in another state often means registering there before anything else. That can include foreign qualification with the secretary of state, a registered agent, a sales tax permit, and payroll accounts. Registration deadlines are separate from tax return deadlines, and some states assess penalties for operating while unregistered.

Income and franchise taxes

Where a business has enough connection with a state, that state may impose an income tax on the portion of income apportioned to it, a franchise tax based on capital or net worth, or a minimum tax simply for being registered. Some states also impose entity-level taxes on pass-through businesses, which is why a partnership or S corporation can owe tax even though income passes through to owners.

Gross-receipts taxes

A handful of states impose a tax measured by gross receipts rather than net income. These can apply even to a business with no profit, and the rules are unrelated to federal taxable income. Businesses expanding into a new state should check whether the state uses this model before assuming a loss year means no liability.

Payroll obligations

Payroll obligations often arrive earlier and hit harder than income tax obligations. They generally include employer registration, withholding on wages sourced to the state, unemployment insurance contributions, new hire reporting, and periodic returns. Failure to register before the first payroll in a state usually produces penalty and interest exposure quickly.

Sales-tax considerations beyond the threshold

Even after registration, the work is not uniform. States differ on which goods and services are taxable, on how shipping is treated, on local rate administration, on exemption certificate handling, and on filing frequency. Service businesses often assume they are out of scope entirely; in some states, specific services are taxable.

Why the rules differ so much

State tax systems are independent. Each state chooses its tax base, its thresholds, its apportionment formula, and its administrative rules, subject to federal constitutional limits. That is why a business can be fully compliant in one state and non-compliant in the state next door with identical activity.

Practical steps

  • Keep a written list of every state where you have people, property, or meaningful sales.
  • Review it whenever you hire, relocate someone, add a warehouse, or open a new sales channel.
  • Track sales by destination state so you can see thresholds approaching rather than discovering them later.
  • Register before you begin activity in a new state, not after.
  • Address a missed obligation early; voluntary disclosure options are often more favorable than waiting for a notice.

If you are already behind in a state, the first step is usually a clean set of records. Our guide to bookkeeping cleanup covers the groundwork.

Talk it through with AEM

Every situation described here depends on facts that are specific to your business. AEM Accounting Solutions reviews your circumstances, explains the options in plain language, and quotes the work in writing before anything starts. You can request a personalized quote or see how engagements are priced on our pricing page.

This article provides general educational information and is not individualized tax, legal, or accounting advice. Tax treatment depends on the taxpayer’s specific circumstances and applicable federal and state law.