Multi-State Income Tax for Agencies: Your Client List Is Your Tax Map

Here's the short answer. If your agency has clients in other states, you may owe income tax in those states, and it has nothing to do with whether you have an office there. Most states now divide up a company's income using one factor only, sales, and most of them assign service revenue to the state where the client receives the benefit of the work. Put those two rules together and your client roster becomes your tax map.

That's the whole mechanism. The rest of this article is where it lives and what to do about it.

I've been a CPA for more than 23 years, and my firm works with more than 70 marketing and advertising agency owners every month. About half of our clients have a multi-state filing requirement. And many of them didn't know it when they came to us.

They weren't careless. They were working with a generalist CPA, somebody who doesn't spend their days inside agency businesses, and nobody had ever asked the question. An owner tells me the agency operates in one state. Then I look at the client list and count seven. Those are two different businesses as far as the tax code is concerned, and only one of them was on the return.

I want to be straight with you about something before we go further. Almost everything written about this topic is written for somebody else. Search "state tax nexus" and you'll get article after article about Amazon FBA warehouses, inventory sitting in states you didn't choose, and the $100,000 sales tax threshold. That's the e-commerce version of this problem. You don't have inventory. You have retainers. The agency version runs on completely different rules, and the articles that would tell you so are the ones nobody writes.

Why Doesn't Your Office Location Decide This Anymore?

It used to. For decades, states split up a multi-state company's income using three factors weighted equally: property, payroll, and sales. If you had 10 percent of your property, 10 percent of your payroll, and 10 percent of your sales in a state, that state taxed 10 percent of your income.

Notice what that old formula did for you. Two of the three factors measured your footprint. Where you owned things and where you paid humans both pulled income back toward home and diluted what any distant state could claim.

That formula is mostly gone. Most states have moved to what's called a single sales factor, which throws out property and payroll completely and divides income on sales alone. Practitioner surveys put adoption at roughly two-thirds of taxing states, with more than 30 states there now and others still converting.

Read that again with an agency in mind. You don't own much: laptops and a lease. And under a single sales factor, your payroll no longer counts toward the split either.

Everything internal drops out of the math. What's left is the client list.

What Does "Where the Client Receives the Benefit" Actually Mean?

Once a state decides to divide income on sales, it needs a rule for which sales are its own. For a company shipping boxes that's easy: the sale goes where the box goes. For a service there's no box to follow, so states picked one of two theories.

Market-based sourcing assigns your fee to the state where the client receives the benefit of the work. You're in one state, your client is in Illinois, the revenue is Illinois revenue. Where your strategists physically sat is irrelevant.

Cost of performance does the opposite. It assigns the fee to the state where the work was performed. Same engagement, and now the revenue stays home with you.

Market-based sourcing won. More than three-quarters of taxing states use it, and states are still converting: Arkansas moved to market-based sourcing for service receipts starting in tax year 2026, and Kansas adopted it effective 2027.

The remaining exceptions are worth knowing precisely because they're exceptions. Delaware, Mississippi, and Texas use a service-performance method, and Alaska, Florida, Kansas, and North Dakota have used cost of performance. Those lists come from practitioner sources rather than from each state's own code, so treat them as a starting point for a conversation, not as a filing position.

What Happens When Two States Claim the Same Retainer?

They both tax it. That's not a bug somebody forgot to fix, and there's no federal referee who sorts it out.

Because states apply different sourcing rules to the same transaction, one dollar of your revenue can be assigned to two states at once, and each one taxes its apportioned share. Your apportionment percentages across all states don't have to add up to 100 percent, and frequently don't.

Here's where it gets genuinely uncomfortable, and I'd rather tell you than let you find out later. "Where the benefit is received" is a judgment call, not a measurement. Say you're running campaigns for a client headquartered in Georgia, aimed at consumers in twenty other states. Where's the benefit received? At their headquarters? In the markets you targeted? Where their customers actually clicked?

States give you differing and sometimes unhelpful guidance on that. Which means you pick a position, and then you defend it.

That's why documentation belongs upstream, in how you record engagements, and not downstream in a scramble next spring. If you can't say which state each retainer was sourced to and why, you don't have a position. You have an assumption. Incorrect revenue sourcing is one of the first things a state looks at in an examination, and thin records are what turn a defensible judgment call into an assessment.

This is the same discipline as measuring agency profitability properly. The number is only as good as what stands behind it.

Doesn't Public Law 86-272 Protect Me?

No. Not even a little, and this is the single most expensive misunderstanding in this whole subject.

Public Law 86-272 is a federal statute from 1959. It bars a state from imposing a net income tax on an out-of-state business when that business's only activity in the state is soliciting orders for sales of tangible personal property, with the orders sent out of state for approval and filled by shipment from outside the state.

Read the words "tangible personal property." That's a physical product. You sell services.

There's no version of the facts where this statute helps an agency. And that matters because 86-272 gets cited constantly in general small-business tax writing as a reason not to worry about out-of-state filings. An owner reads that, relaxes, and has drawn exactly the wrong conclusion. Consultants, SaaS companies, IT firms, and agencies all tend to believe they're covered. Most are not.

One more piece, because it surprises people who do qualify. Even where the statute applies, it doesn't turn off a state's minimum fees. California's Franchise Tax Board says it plainly on its own website: a business protected under 86-272 is exempt from taxes based on net income, but it "still may be considered to be doing business in California and may be liable for filing and paying the applicable amounts."

The federal safe harbor was always narrow. For you, it's simply absent.

How Much Sales Volume Triggers a Filing Requirement?

It depends on the state, and the number is lower than most owners guess.

Many states use a bright-line test with dollar thresholds for in-state property, payroll, and sales. The model version, adopted by the Multistate Tax Commission back in 2002, uses $50,000 of property, $50,000 of payroll, $500,000 of sales, or 25 percent of your total of any one of those. Connecticut, Massachusetts, Michigan, Colorado, and California all took some version of it.

California is the clearest worked example, and these figures come straight from the FTB's own table under Revenue and Taxation Code section 23101. You're "doing business" in California if your California sales, property, or payroll exceeds the lesser of a threshold amount or 25 percent of your total. The thresholds get indexed for inflation every year:

• 2025: $757,070 of sales, or $75,707 each of property and payroll
• 2024: $735,019 of sales, or $73,502 each of property and payroll

California hadn't published the 2026 indexed figures when I wrote this, so check the current year before you rely on a number. And notice the 25 percent test sitting next to the dollar figure. A smaller agency can cross on the percentage long before it ever approaches $757,070.

Now the detail almost nobody mentions, and it's the one that matters most to you. FTB's guidance says that if you own a partnership, an LLC taxed as a partnership, or an S corporation, you include your distributive share of that entity's sales, property, and payroll when you test the thresholds.

Most agencies are S corporations or partnerships. Which means this analysis doesn't stop at the company. It follows the income onto your personal return.

Does Crossing a Threshold Mean a Big Tax Bill?

Usually not, and I don't want to sell you a fire that isn't burning.

Here's what typically happens. A state finds it can tax you, you apportion a modest slice of income there, and the tax on that slice is small. What you also get is a minimum franchise or entity fee for the privilege of being in the jurisdiction, plus the cost of preparing another return. That's the real arithmetic in most states most of the time.

So the problem isn't the size of the bill. The problem is what happens when the bill never gets filed.

Nobody sends you a notice the month you create a filing obligation. You find out years later, when cross-state data matching or a nexus questionnaire surfaces it, and by then you're looking at unfiled returns plus penalties plus interest for every one of those years. A state's assessment window on an unfiled return is often unlimited. That's the number that gets big, and it gets big quietly.

That's the difference between a compliance conversation and a planning conversation, and it's the same reason waiting until tax season to talk to your CPA costs money. The exposure builds while nothing appears to be happening.

Who Should Ignore This Article?

Fair question, and there are real answers.

If every client you have is in your home state, this doesn't apply to you. Single sales factor plus market-based sourcing sends all your revenue to one place, which is where you already file. Come back when you sign your first out-of-state client.

If you're a solo operator with two local clients, the mapping exercise below takes fifteen minutes and will probably come back clean. Do it once so you know, then get back to work.

If your out-of-state revenue is genuinely tiny, the honest answer may be that a filing obligation exists and isn't worth chasing yet. That's a judgment call about materiality, and it's a legitimate one to make deliberately with your advisor. What's not legitimate is making it by accident because nobody looked.

The agencies that need this are the ones with a real roster spread across states, where the numbers are big enough that ignoring them compounds.

What Should You Do About It?

Three steps. None of them require you to become a state tax expert.

1. Pull revenue by client state for this year and last. You already have this. It's in your books, sorted by client, and it takes an afternoon at most. You're not looking for precision to the dollar. You're looking for which states have meaningful numbers attached to them.

2. Check those states against their own thresholds and sourcing rules. Two questions per state: does my revenue there cross the line, and does this state source my kind of revenue to the client's location or to mine? This is where an advisor who does it regularly saves you real time, because the answer is state-specific and the rules move.

3. Look back three to five years before you register anywhere. If you crossed a line in a prior year and never filed, most states run voluntary disclosure programs that cap the lookback period and waive penalties in exchange for coming forward. That option is worth real money and it disappears the moment the state contacts you first. So the order matters: find out, quantify it, then decide, and register after that rather than before.

One more thing to put on the list rather than solve today. If you're an S corporation or a partnership, most states now offer a pass-through entity tax election that lets the business pay state tax at the entity level and work around the federal cap on deducting state taxes. Once you're filing in five states, that stops being one decision and becomes five. It deserves its own conversation, and it's a genuine opportunity rather than another compliance chore.

Frequently Asked Questions

Does having clients in another state mean I owe income tax there? It can, and for most states it's the deciding factor. Most states now apportion business income using sales alone and source service revenue to where the client receives the benefit of the work. So out-of-state clients can create both a filing obligation and apportioned income in their state, regardless of where your office is.

Is this the same as sales tax nexus? No, and mixing them up is common. Sales tax, income tax, franchise tax, and payroll withholding each carry their own separate nexus standard, and each varies by state. You can have no sales tax obligation in a state and still owe an income tax return there.

Does Public Law 86-272 protect my agency? No. The statute only covers solicitation of orders for tangible personal property. Services fall entirely outside it, so an agency gets no protection from it at all.

What if my client is a national brand operating in twenty states? Then "where the benefit is received" is a genuine judgment call, and you make it rather than the state. Pick a defensible position, apply it consistently across engagements, and keep records showing how you reached it.

What happens if I should have been filing and wasn't? Most states run voluntary disclosure programs that cap how far back you have to go, generally three to five years, and waive penalties in exchange for coming forward. Eligibility usually ends once the state contacts you, so the value of that option decays with time.

Do I need to worry about this if my out-of-state revenue is small? Possibly not in dollar terms, but you should know the answer instead of assuming it. The risk isn't a big tax bill, it's years of unfiled returns compounding quietly while nothing appears to be wrong.

The Bottom Line

Your agency's tax map isn't drawn by your lease. It's drawn by your client list, because the formula that divides your income now runs on sales alone, and your sales follow your clients.

That's not a reason to panic. It's a reason to look, once, deliberately, and know where you stand before a state tells you.

If you'd rather start on your own time, I wrote a book for marketing and advertising agency owners. You can request a free copy at the link below.

https://www.craigcodyandcompany.com/free-book

And if you've got remote humans on payroll in other states, that's a separate trigger with its own rules. I wrote that one up separately, because where your people sit creates obligations that have nothing to do with where your clients sit.

Craig S. Cody, CPA, is a Certified Tax Coach and a former NYPD Lieutenant. His firm works with more than 70 marketing and advertising agency owners every month, helping them keep more of what they make through proactive tax planning.

This article is general information, not tax advice for your specific situation. State rules change frequently and the figures here carry the year they applied to. Confirm current-year thresholds and your own facts with your advisor before acting.