Picture a two person operation that has filed federal returns correctly for six years, keeps clean records, and pays a preparer who has never raised a concern. In the seventh year an envelope arrives from a state where the business did four jobs, asserting that it should have been registered, collecting, and filing all along. Nothing about the federal side was wrong. The trouble is that state and local obligations are set by thousands of separate authorities, none of which coordinate, and no single agency has any responsibility for telling a small business which of them apply.
Why There Is No Single Answer to This
Every state writes its own rules, and beneath the states sit counties, cities, and special districts that levy their own taxes and issue their own licenses. A business operating in three states may face three sets of registration requirements, three filing calendars, three definitions of what is taxable, and a handful of municipal licenses that exist independently of all of it. None of these authorities knows about the others and none is obliged to. A business can be entirely current with one and unknown to the next, in the same county, in the same year.
What follows from that is a peculiarity people find hard to accept: nobody is going to tell you. Federal registration produces mail, reminders, and a preparer who asks questions. State and local obligations frequently produce nothing at all until an assessment arrives, because the first contact many agencies have with a small out of state business is the point at which they have identified one that never registered. Silence is not evidence of compliance in this area, and it is treated as such constantly.
What Actually Creates an Obligation in a State
The general principle is a connection substantial enough that the state can require participation in its system, and the connection is easier to create than most people expect. An office, an employee, or inventory stored in a warehouse are the obvious versions. Less obvious are a single employee working from home in another state, a truck and crew performing work there for a period of weeks, or a contractor pulling a permit under a local jurisdiction that ties licensing to tax registration. That last route catches contractors constantly, since pulling a permit is frequently the moment a jurisdiction first learns the business exists.
Selling into a state without ever entering it can also create an obligation, since most states now set thresholds based on sales volume or transaction counts rather than physical presence. Those thresholds vary considerably and the counting rules differ, so a business that crosses one in a single busy quarter may acquire a filing obligation it will carry for years. Checking annually against the states that produce meaningful revenue is a short exercise and it is the one most operations never perform.
The Three That Catch Small Operations
Sales tax on services is the first, because most people believe services are not taxable and in a growing number of states some of them are. Which services, and under what circumstances, differs enough between neighboring states that experience in one is actively misleading in the other. A repair that is exempt on one side of a state line is frequently taxable on the other, and the customer will not know either. Charging tax that is not owed causes its own trouble, so the answer is worth establishing rather than guessing in either direction.
Payroll withholding for a remote worker is the second, and it arrived with almost no publicity. An employee living and working in a different state generally creates a registration and withholding obligation there from the first paycheck, regardless of company size. The third is the municipal license: a city business license, a home occupation permit, or a local gross receipts tax that no accountant reviewing a federal return would have any reason to mention. The federal directory at USA.gov is the least frustrating starting point for finding which office in a given state or city actually administers each of these, since the naming conventions differ everywhere.
What the Letter Usually Says
An assessment for unregistered activity typically covers several prior years, includes estimated tax based on whatever information the state has assembled, and adds penalties and interest to the estimate. The estimate is frequently high, because the state is working without records and has no incentive to guess low, and the letter states a deadline for responding that is short relative to the work involved in responding properly, which is itself part of why so many of these end badly.
The important feature of these letters is that the estimate is almost always negotiable downward on production of actual figures. A business that can show what it genuinely sold in that state, with invoices and returns to support it, is usually assessed on the real number rather than the estimate. Ignoring the letter converts a negotiable estimate into a final assessment, which is the single worst available outcome and also the most common one. Responding by the deadline, even with a short letter saying that records are being assembled and asking for time, preserves everything that matters.
Getting Current Without Making It Worse
Most states operate a voluntary disclosure process, and it exists because states would rather collect than pursue. Approaching a state before it approaches you typically limits the number of prior years assessed and abates most or all of the penalties, and it is frequently done through a representative without naming the business until terms are agreed. That option disappears the moment a letter arrives, which is the whole argument for acting on a suspicion rather than waiting for confirmation.
The practical version for a small operation is an annual review of where work was actually performed, where employees actually sat, and which states produced meaningful sales. That review takes an hour and answers the only question that matters, which is whether anything changed. The business in that seventh year had not done anything wrong in the ordinary sense. It had simply assumed that a system which sends reminders about one obligation would send reminders about the others, and no part of this arrangement works that way.