Doing business in another state does not trigger one rule - it can trigger up to three separate ones, decided by different agencies under different tests. Registering your business to do business there (foreign qualification), owing that state's income or franchise tax (income tax nexus), and withholding payroll tax for an employee who works there (payroll withholding) are each judged on their own facts. You can owe one without the others, or all three at once. If you've already looked at sales-tax nexus, think of this as its income-tax and payroll cousin - related, but governed by different tests and different thresholds.
Three different questions, three different agencies
It helps to keep these separate in your head, because the state agencies keep them separate too:
Registering to do business (foreign qualification). If you're actively transacting business in a state where your LLC or corporation wasn't formed, that state's corporate law generally requires you to register there as a "foreign" entity - a filing with the Secretary of State, not the tax agency. This is a legal-existence question, not a tax question. What counts as enough activity to require it is set by each state's own statute, and the fee and the annual-report duty that follow vary by state.
Income or franchise tax nexus. Separately, that state's revenue department decides whether your business has enough connection to it to owe income tax, franchise tax, or both - regardless of whether you ever filed a foreign qualification.
Payroll withholding and unemployment tax. Separately again, if you have an employee physically working in that state, its revenue and workforce agencies generally require you to withhold that state's income tax from their wages and pay into its unemployment insurance system.
A business can clear one hurdle and still trip on another. A company that never opens an office anywhere can still create income tax nexus in a state purely through the volume of sales it makes there, or through a single remote employee.
One practical consequence worth knowing: in most states, a business that should have qualified as a foreign entity and didn't can be barred from bringing a lawsuit in that state's courts until it registers and pays whatever back fees or penalties apply. That can be a genuinely bad surprise if you need to sue a customer who hasn't paid you. The details - and how easily the problem is cured - vary by state.
What creates income tax nexus in another state
Income tax nexus has traditionally followed physical presence: an office, a warehouse, inventory stored in the state, or an employee working or regularly traveling there. That remains a classic trigger.
Since the Supreme Court's 2018 decision in South Dakota v. Wayfair opened the door to economic nexus for sales tax, a number of states have applied similar logic to income and franchise tax - meaning a business can owe tax in a state based on the dollar amount of sales made into it, with no property, employee, or office there at all. Some states use a bright-line sales figure (often called a factor-presence standard); others fold the question into a broader "doing business" standard. Whether a given state applies an economic test to income tax, and what the threshold is, varies significantly and these thresholds are adjusted from time to time. There is no single national number to memorize - confirm the current threshold directly with each state's department of revenue.
Public Law 86-272: a narrow federal shield
One federal law cuts against that trend, but it's narrower than most business owners assume. Public Law 86-272 protects an out-of-state business from a state's net income tax if its only activity in that state is soliciting orders for tangible personal property, where the orders are sent outside the state for approval and the goods are shipped in from outside the state. That's the whole scope. The protection does not extend to:
Selling services, consulting, or anything that isn't tangible goods
Software as a service, licensing, or digital products
Activities beyond pure order-solicitation - repairs, installation, collecting on delinquent accounts, local credit approval, and similar activity
Just as important, the shield is only against net income tax. It does not protect you from a state's sales tax collection duty, from gross-receipts or business-activity taxes that aren't structured as net income taxes, or from the separate duty to qualify your entity with the Secretary of State. Owners routinely assume Public Law 86-272 means "no filings in that state." It doesn't.
Internet activity is a genuinely unsettled area. Several states have adopted guidance treating common website functions - things like cookies that track customers in the state, post-sale online chat support, or gathering data through your site for product development - as going beyond protected solicitation, which can create nexus for a business with no physical footprint. That guidance has been challenged in court, has been applied inconsistently from state to state, and the law here is still moving. If your business sells services or software, or does substantial business online, don't assume Public Law 86-272 protects you - check the state's current published guidance and verify your position with a CPA familiar with multistate tax.
Apportionment: how much of your income each state can tax
Having nexus in a state doesn't mean that state taxes 100% of your income - it means the state gets to tax its share, calculated under an apportionment formula. Many states weight the formula heavily or entirely toward sales; others also factor in payroll and property. Formulas and weightings differ by state, so the same total income can be apportioned differently depending on where you have nexus.
A related wrinkle is the throwback rule, which some states apply: if you ship a sale into a state where you aren't taxable (say, because Public Law 86-272 protects you there), a throwback rule can pull that sale back into the sales factor of the state the goods shipped from, instead of letting it drop out of every state's numerator. A throwout rule handles the same situation differently, by removing the sale from the denominator. Not every state has either rule, and the states that do apply them differently - this is genuinely a state-by-state question worth putting to your CPA or the relevant revenue department directly.
The remote employee problem
One of the most common ways a small business accidentally acquires multistate obligations is by letting a single employee work remotely from another state - often without the owner realizing what it triggers. An employee physically working in a state typically creates:
Withholding duties - you generally must register to withhold that state's income tax from the employee's wages
Unemployment insurance duties - you generally must register and pay into that state's unemployment system for that employee
Income tax nexus for the business itself - an employee's presence is a classic physical-presence trigger, independent of any economic nexus threshold
Some neighboring states have reciprocity agreements that let a resident of one state work in the other without having the work state's income tax withheld. These agreements are limited: they cover only specific state pairs, they generally address income tax withholding only, and they typically do not change your unemployment insurance obligations, which follow where the work is actually performed. Ask both states' tax and workforce agencies whether an agreement applies to your situation rather than assuming it does.
If a remote hire is new territory for you, the payroll and registration side is worth working through deliberately before the first paycheck, not after. And if that worker is a contractor rather than an employee, remember that classification is a legal test based on the real working relationship - not a label you choose - and getting it wrong creates back-tax and wage exposure of its own.
What this means for pass-through owners
If your business is a sole proprietorship, partnership, or an LLC or S-corp taxed as a pass-through, the business's income flows onto your personal return. When that business has nexus in more than one state, you as the owner can end up needing to file nonresident (or part-year) personal income tax returns in each of those states on your share of the income - separate from anything the business itself owes. Many states offer a composite return or a pass-through entity tax election that lets the business file and pay on the owners' behalf instead, which can simplify matters; whether that option exists, and how it works, varies by state. This is a conversation to have with a CPA before you expand into a new state, not after.
What to do
Map every state where you have a connection - an office, stored inventory, a remote employee, regular travel by an owner or salesperson, or a meaningful volume of sales.
Check foreign qualification requirements with the Secretary of State (or equivalent) in each state where you're actively doing business.
Check income and franchise tax nexus rules with each state's department of revenue, including whether it applies an economic or factor-presence threshold and whether Public Law 86-272 realistically protects your business there.
Register for withholding and unemployment insurance in any state where an employee physically works - even one employee.
Ask a CPA about apportionment and PTE elections before you file, especially once you have nexus in more than a state or two.
Don't wait for a notice. States generally expect registration at or before the point you begin doing business or hiring there, and late registration can carry penalties and back-tax exposure. The exact deadlines, thresholds, and penalties vary by state and change - confirm the current ones directly with each state's tax agency and Secretary of State rather than assuming you're in the clear.
If the cost of professional help is the thing stopping you, free official help exists: the SBA (sba.gov), SCORE, and your state's Small Business Development Center can talk through multistate expansion with you at no charge, and the IRS (irs.gov) and each state's revenue department publish their own guidance directly.
This article is general business information, not legal, tax, or financial advice, and does not create an attorney-client or accountant-client relationship. Multistate tax rules change frequently and vary by state - confirm current thresholds, forms, and deadlines with each state's Secretary of State and tax agency, or talk with a CPA experienced in multistate taxation, before you register or file.
Frequently asked questions
If I just have a few customers in another state, do I owe that state income tax?
Not automatically. If you're selling tangible goods and your only activity there is soliciting orders that are approved and shipped from outside the state, Public Law 86-272 may shield you from that state's net income tax even though you have customers there. But if you sell services, software, or anything beyond basic order-taking - or if your sales into that state cross the threshold it uses for income tax nexus - you can owe income or franchise tax with no office or employee in the state at all. And the federal shield never covers sales tax or gross-receipts taxes. The rules vary sharply by state, so check with that state's tax agency.
I formed my LLC in one state. Do I need to register anywhere else?
Possibly, if you're actively doing business in another state - that's a foreign qualification with that state's Secretary of State, and it's a separate question from income tax nexus and payroll withholding. Each is decided under its own rules, so qualifying in a state doesn't automatically mean you owe income tax there, and owing income tax somewhere doesn't automatically mean you need to qualify. What counts as "doing business" enough to require qualification is defined by each state's own corporate statute, so check that state's Secretary of State.
One employee works remotely from another state. Do I really have to register there?
Usually, yes. An employee physically working in a state typically creates withholding tax and unemployment insurance obligations in that state, and it can create income tax nexus for the business too. This applies even if that employee is your only connection to the state. The specific triggers, forms, and deadlines vary, so check that state's tax and workforce agencies for the exact registration steps.
Is sales tax nexus the same as income tax nexus?
No - they're decided separately, sometimes with different thresholds and different triggers, even within the same state. Meeting one doesn't automatically mean you've met the other. Treat them as two separate questions and check each state's rules for both.
What is apportionment and does every state use the same formula?
Once a state has the right to tax your business income, apportionment is the formula it uses to decide how much of your total income counts as earned there - commonly based on sales, and sometimes also payroll and property. States use different formulas and weightings, and some apply a throwback rule that pulls a sale back into the sales factor of the state the goods shipped from if you weren't taxable in the destination state. Confirm the formula with each state's tax agency or a CPA familiar with multistate returns.
This article is general legal information, not legal advice, and may not reflect the most current law or the law in your jurisdiction. Laws vary by state and change over time. For advice about your specific situation, consult a licensed attorney.
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