The 12 Biggest Tax Mistakes That Cost Marketing and PR Agency Owners Thousands

By Craig S. Cody, CPA, Certified Tax Coach.

Here's the answer up front. Your tax return can be a hundred percent correct and still cost you money, because a return only records decisions you already made. I wrote a book with this title, I've reviewed hundreds of marketing and PR agency tax returns since, and the same twelve show up over and over. Eleven of them are decisions you make before the year closes. The twelfth is about who's making them with you.

Why Does a Correct Tax Return Still Cost You Money?

Because tax preparation and tax planning are two different products, and most agency owners have only ever bought one.

Here's the picture I use in the book. Most tax professionals drive using the rearview mirror. They do a perfectly decent job recording the history you hand them. They don't do much, if anything, to help you write a new one, the kind that costs you less in the taxes we all hate to pay.

That's the whole distinction. A preparer can be excellent and still hand you an expensive year, because by the time the return exists every decision that set the number has already been made.

Mistakes 1 and 2: Are You Planning, or Just Filing?

1. Failing to Plan

The first mistake is the biggest mistake of all, and everything else on this list is a symptom of it.

There's a test that settles it quickly. In the last twelve months, did your accountant call you with an idea, before you called them with a deadline? If the answer is no, you have a preparer. Preparers are necessary. They are not the same purchase.

What it costs: every other item below. The fix: know which product you're buying, and price it accordingly. A CPA should be an income item, not an expense.

2. Audit Paranoia

The second mistake is nearly as important as the first: fearing the IRS rather than respecting it. Agency owners skip deductions they've genuinely earned because somebody warned them about raising a red flag.

Audit rates are far lower today than the historic peak, and lower than when I wrote this chapter. A legitimate deduction with documentation behind it has very little to fear. Reporting structure matters too: pass-through entities have historically drawn audit attention at a small fraction of the rate that sole proprietorships do at comparable income, which means how you're organized affects your exposure as much as what you claim.

And if you ever do disagree with an outcome, there's a real appeals path, including a small-case division of the U.S. Tax Court for disputes under $50,000.

What it costs: every deduction you were entitled to and didn't take. The fix: if an advisor tells you to skip something, make them explain exactly why. "It'll raise a red flag" is not an explanation. It's your money on the table, not theirs.

Mistakes 3 to 5: Is Your Agency Structured and Funded Right?

3. The Wrong Business Entity

Most agencies start as a sole proprietorship, add an LLC or a corporation as they grow to limit liability, and then never revisit the decision. The entity that was right at founding frequently isn't right at scale.

The tax stakes are concrete. A sole proprietor pays self-employment tax at roughly 15.3% on all net business income. An S corporation splits the same money into a reasonable W-2 salary and distributions, and the distributions are not subject to self-employment tax. The 2026 Social Security wage base is $184,500, which is where the larger half of that 15.3% stops applying to salary.

An LLC is not a tax entity at all, which is the part owners find most surprising. A single-member LLC is taxed as a proprietorship unless it elects otherwise; a multi-member LLC chooses partnership or corporate treatment. The liability wrapper and the tax treatment are separate decisions, and you can change the second without disturbing the first.

What it costs: four figures a year at modest profit, five once the agency is real. The fix: re-run the entity analysis at your current numbers, not the numbers you had when you formed.

4. Missing Qualified Business Income

The 20% deduction on pass-through business income, and this is the chapter where the law has moved most since I wrote it.

Three updates matter. First, the deduction is permanent. The old sunset provision, which said the section simply would not apply to tax years beginning after December 31, 2025, was repealed outright by Public Law 119-21 and replaced with something else entirely. If you accelerated income or restructured because the deduction was going away, you planned around something that isn't happening.

Second, the rate is still 20 percent. You may see 23 percent quoted, and it is worth knowing why: 23 percent was in the House-passed version of the bill and it did not survive into the enacted law. The statute reads 20 percent.

Third, and this is the part that matters specifically to this audience: the deduction phases out for "specified service trades or businesses," and advertising and marketing are not among the enumerated fields. The regulation lists thirteen: health, law, accounting, actuarial science, performing arts, consulting, athletics, financial services, brokerage, investing and investment management, trading, dealing in securities, and any business whose principal asset is the reputation or skill of its owners or employees. Advertising and marketing appear on none of them. Better still, the regulation expressly carves "sales, or economically similar services" out of the consulting category. So agencies often keep the full deduction at income levels where law, accounting and consulting firms lose it.

That's a real structural advantage and most agency owners don't know they have it.

The caveat is genuine and you should take it seriously. If a meaningful share of your revenue is billed as consulting rather than as advertising or marketing services, the analysis changes. Look at what your own engagement letters and invoices actually say. The label is not cosmetic here.

Two smaller changes came in with the same law and both help. The phase-in range widened from $50,000 to $75,000 for single filers, and from $100,000 to $150,000 joint, which softens the cliff for anyone near a threshold. And there's now a minimum deduction of $400 for a taxpayer with at least $1,000 of qualified business income, which matters more to a side business than to an established agency.

What it costs: 20% of qualifying profit, every year you don't claim it correctly. The fix: confirm your classification with somebody who has read the regulations, and make sure your invoicing supports the position.

5. The Wrong Retirement Plan

The plan you choose sets your ceiling, and the ceilings are not close to each other. For 2026: a SIMPLE IRA caps your own salary deferral at $17,000. A 401(k) takes $24,500. Add a profit-sharing contribution and the total that can land in that 401(k) account reaches $72,000. And a defined benefit or cash balance plan is measured against an annual benefit limit of $290,000, which is a different universe. The book has a chart comparing the first three and the gaps were wide then too.

But contribution limits aren't the whole question. You're choosing among contribution room, flexibility and liquidity, and the right answer depends on your payroll and your age as much as your profit.

For an owner with the right profile, layering profit sharing onto a 401(k), and then a cash balance plan on top of that, is a different order of magnitude entirely. I've had many clients put an additional $100,000 or more away every single year using that structure. Agencies are unusually good candidates, because a payroll of well-compensated senior people is the profile these plans are designed around.

What it costs: for a profitable owner in their forties or fifties, this is very likely the largest single number on this page. The fix: ask what your ceiling is. Don't ask what's quickest to open.

Mistakes 6 and 7: Are You Missing the People Around You?

6. Missing Family Employment

Hiring your children shifts income from your bracket to someone who pays less, and their own standard deduction wipes out the first tranche entirely, even though you still claim them as dependents. For 2026 that is the first $16,100 of earned income taxed at nothing. The book's figure was $12,000, which was the 2018 number.

The requirements are specific and they're what make it hold up:

• Pay a reasonable wage for real work. The Tax Court standard is what you'd pay a commercial vendor for the same service, adjusted for the child's age and experience. If your fifteen-year-old maintains the agency's website, ask what a freelance developer would charge.
• Write a job description and keep a timesheet.
• Pay by check, into an account in the child's name.
• The account can be a Roth IRA, a 529, or a custodial account. It cannot be used for your own obligations of parental support, though private school and summer camp are not parental support obligations.
• In an unincorporated business, you don't withhold Social Security for a child under 18.

A Roth IRA opened in a fifteen-year-old's name has decades of tax-free compounding ahead of it, which is a larger long-run number than the deduction that funded it.

What it costs: the spread between your bracket and theirs, on every dollar you could have shifted. The fix: document it like the employment arrangement it is.

7. Missing Medical Benefits

Health care has overtaken taxes as the expense agency owners worry about most, and the tax code is unhelpful about it by default. Your unreimbursed medical costs only count on Schedule A above 7.5% of adjusted gross income, and most households never clear that threshold. The deduction is simply lost.

A Medical Expense Reimbursement Plan under Section 105 moves that spending to the business side, where it's deductible to the agency and non-taxable to the recipient, with no percentage floor in the way.

The catch is who the code counts as an employee, and it's the reason this gets explained badly. If you operate as a proprietorship, partnership, LLC or S corporation, you are treated as self-employed and cannot receive plan benefits yourself. The structure has to be designed around that fact. Depending on your entity that can mean delivering benefits through a bona fide employed spouse, or using a different vehicle entirely. For your own health premiums as a more-than-2% S corporation shareholder, the route is a specific three-step method through your W-2, and the deduction is capped by your Medicare wages rather than your total wages, which catches owners who take a small salary.

What it costs: every out-of-pocket medical dollar in a household with real dental, vision or orthodontic spending. The fix: design the entity and the plan together.

Mistakes 8 to 11: Which Deductions Are You Sitting On?

8. Missing a Home Office

Home office expenses are probably the most misunderstood deduction in the entire tax code. For years taxpayers believed claiming one guaranteed an audit, and plenty of tax professionals were happy to let that myth stand. The Supreme Court made the deduction easier to qualify for in 1994 and Congress made it easier again in 2007.

It qualifies if it's your principal place of business, if you use it to meet clients or prospects in the normal course of business, or if it's a separate unattached structure. Most qualify under the first test, and Publication 587 defines that as exclusive and regular use for administrative or management activities with no other fixed location where you do substantial administrative work. Having another office doesn't disqualify you, as long as you don't regularly do the administrative work there.

Here's what changed since the book. If you run an S corporation, the employee version of this deduction is permanently gone. You reach the same money through an accountable plan reimbursement instead: the company pays you back for the business-use share of your actual home operating costs, deducts it, and the reimbursement isn't taxable to you or subject to payroll tax.

What it costs: usually four figures a year, on a space you already pay for. The fix: adopt an accountable plan in writing before the reimbursements start.

9. Missing Car and Truck Expenses

The mistake here isn't forgetting the deduction. It's calculating it the wrong way.

The standard mileage allowance is easier, which is exactly why it gets chosen, and for a lot of vehicles it's less than what the car actually costs to operate. AAA publishes annual operating-cost research and it frequently exceeds the allowance, which means every mile is losing you money.

It starts with business use percentage, and the code splits your trips three ways: business, commuting and personal. Commuting and personal are not deductible. Home to your first stop and last stop to home are personal. A stop where you perform no service, the bank or the post office, doesn't make a trip business. And putting your agency's logo on the vehicle does not convert commuting miles into business miles, which the IRS says explicitly.

There are four accepted ways to track it: log every mile for the year, log a representative 90-day period, log the first week of each month, or record start and end odometer readings for 90 days and treat everything that isn't personal or commuting as business. Log at least weekly and keep receipts above $75.

Then you choose between the allowance and actual expenses. Watch the rate this year, because it changed mid-year: 72.5 cents through June 30 and 76 cents from July 1. Generally the more you drive the better the allowance does, because it assumes a fixed depreciation component that heavy mileage outruns.

One trap worth knowing: if you own the vehicle you can switch from the allowance to actual expenses later, but you cannot switch from actual expenses back to the allowance, and you can't use the allowance at all if you lease and started on actual, or if you run five or more vehicles.

What it costs: the gap between the two methods, every year, compounding if you picked wrong at the start. The fix: run both. It's arithmetic, not judgment.

10. Missing Meals and Entertainment

You can deduct 50% of a meal with a bona fide business purpose, so long as it isn't lavish. And ask yourself honestly when you last ate with someone who wasn't a client, a prospect, a referral source or a colleague. In this business the answer is often "I can't remember."

What counts: food, drinks, tax, tip, coat check and valet. You generally can't deduct a meal with your spouse unless you're traveling for business together, though you can include a spouse when your guest brings theirs.

Documentation is lighter than most owners assume. No receipt required under $75, but five things have to be recorded: how much, when, where, your business relationship with the guest, and the business purpose. A credit card statement covers the first three; the last two need a log.

Two things owners routinely miss. You don't have to eat out. Business meals you host at home are deductible on the same rules, and if you have more than a dozen guests you can deduct reasonable costs where the primary purpose is business. And meals that are integral to a sales seminar or similar event can reach 100% rather than 50%.

One thing to be clear about, and the book says it too: entertainment is gone. Tickets, ball games, concerts, the whole category was eliminated by the Tax Cuts and Jobs Act of 2017. If anyone is still telling you to deduct client entertainment, they're working from pre-2018 rules.

While we're here: business gifts are deductible up to $25 per recipient per year, married couples counting as one. Advertising specialties under about $4 each don't count against it.

What it costs: half of a category you're already spending in. The fix: the five-item log, and stop trying to deduct entertainment.

11. Missing Depreciation and Amortization

When you buy capital equipment, you depreciate it over a period approximating its useful life. Asset class sets the speed; computers are five-year property. Business use percentage sets how much. Above 50% business use you generally qualify for accelerated depreciation; at or below it you're on straight-line.

First-year expensing lets you deduct the whole cost in the year you buy instead. It's available on property placed in service as late as December 31, requires business use above 50%, and can't exceed your taxable income from the activity, though unused amounts carry forward. The 2026 Section 179 limit is $2.5 million with a dollar-for-dollar phase-out above a much higher threshold, which means it's effectively unlimited for an agency.

The schedule in my book is out of date, and in your favor. It describes bonus depreciation stepping down to 20% by 2026 and disappearing in 2027. That's no longer the law: full first-year bonus expensing was restored for qualified property placed in service after January 19, 2025.

Remember the other side. When you sell property you expensed or depreciated, your basis is cost less what you deducted, and gain comes back as ordinary income through recapture. Expense a $2,000 computer, sell it for $600, and that $600 is ordinary income.

On the intangible side, when you acquire another agency, goodwill is amortized over 15 years. Allocate $150,000 of a purchase price to goodwill on a January 1 closing and that's $10,000 of first-year amortization, separate from any depreciation on the assets.

What it costs: timing, which is cash. The fix: decide expensing versus depreciation deliberately each year, with an eye on what you plan to sell.

What Is the 12th Mistake?

12. Missing My Help

In the book I call the twelfth mistake failing to take advantage of my help, and I put it last on purpose.

Eleven of these you can look up. You could read the chapters, take notes, and do a creditable job on most of them yourself. The twelfth is different in kind: it's about whether anyone is running the other eleven before the year closes rather than after.

What that actually looks like is unglamorous. I sit down with you and your most recent returns and walk through them item by item. I look at how you make your money and where you spend it. Then it goes into a plan that gets you where you want to go in the most tax-efficient way the law allows.

I can't tell you what you'll save before I've seen your returns, and I won't pretend otherwise. What I will say is that everything we recommend is court-tested, and it beats driving by the rearview mirror.

Which One Should You Fix First?

In this order, because each makes the next cheaper:

1. Entity, at your current numbers (3). Everything else sits on top of it, and it also affects your audit exposure (2) and your QBI position (4).
2. QBI classification (4). Confirm it. It may be worth 20% of profit and it's frequently misapplied to agencies.
3. The retirement plan ceiling (5). Largest dollars on the page for most profitable owners.
4. Plan documents (7, 8). Section 105 and the accountable plan both have to exist before the spending they cover. This is the one that punishes procrastination hardest.
5. The tracking decisions (9, 10, 11). Mileage method, the five-item meal log, expensing versus depreciation. Cheap to set up, and they only work prospectively.
6. Family employment (6), if you have kids old enough to do real work.
7. Then the frame (1, 2). Put a date on the calendar mid-year and stop letting "red flag" end a conversation.

Who This Isn't For

If your agency is pre-profit, most of this is premature. Entity elections and plan documents cost money to maintain and should follow profit, not anticipate it.

If you already work with a proactive advisor who called you in June with an idea, you're probably clear on eight or nine of these. Read 4 and 7 anyway. The QBI classification question is the one that gets assumed rather than checked, and the Section 105 entity trap is the one that gets explained wrong by people who mean well.

Frequently Asked Questions

What is the single biggest tax mistake a marketing agency owner makes?

Failing to plan. It's the first chapter of my book and I'd still put it first, because every other mistake on the list is a symptom of it. Planning is the only one that has to be fixed first, since it's what creates the chance to fix the other eleven.

Does claiming a home office deduction increase my audit risk?

No. That belief is itself one of the twelve mistakes. The Supreme Court eased the qualification standard in 1994 and Congress eased it again in 2007. What does matter is the lane: if you run an S corporation, the employee version of the deduction is permanently gone, so the money reaches you as an accountable plan reimbursement rather than a deduction.

Do marketing and advertising agencies qualify for the qualified business income deduction?

Generally yes, and more fully than many professional firms. Advertising and marketing are not usually treated as a specified service trade or business, so the deduction doesn't phase out with income the way it does for law, accounting or consulting practices. If a meaningful share of your revenue is billed as consulting, get the classification confirmed before relying on it.

Can an S corporation owner be reimbursed through a Section 105 medical plan?

Not personally. An owner of a proprietorship, partnership, LLC or S corporation is treated as self-employed and cannot receive plan benefits. Your own premiums run through a specific three-step method on your W-2 instead, and the deduction is capped by your Medicare wages rather than your total wages.

Should I use the standard mileage rate or actual vehicle expenses?

Run both, because it's arithmetic. The allowance is easier and generally favors high mileage; actual expenses generally favor an expensive vehicle driven less. Two constraints matter: you can switch from the allowance to actual expenses if you own the vehicle, but you cannot switch back, and you can't use the allowance with five or more vehicles.

Can I still deduct client entertainment?

No. The Tax Cuts and Jobs Act of 2017 eliminated the entertainment deduction entirely. Business meals with a bona fide business purpose remain 50% deductible, and meals integral to a seminar or similar event can reach 100%, but tickets, games and concerts are gone.

When is the right time to talk to a tax advisor about all of this?

The middle of the year you're being taxed on. That's when entity, plan adoption, income timing and purchase timing are all still adjustable. By the following spring, nearly every decision that set the number has already been made.

Let's Talk

None of these twelve is a trick. Every one of them is in the code, and every one is available to you. It just doesn't happen by itself.

If you want to know which of the twelve are yours, that's a specific answer, and it takes reading your actual returns.

Book a Free Tax Analysis

Or request a free copy of the book and check yourself against all twelve first.

Filing a return isn't a tax strategy.

Craig S. Cody, CPA, is a Certified Tax Coach and a former NYPD Lieutenant. He is the author of The 12 Biggest Tax Mistakes That Cost Agencies Thousands. 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. Confirm your own facts with your advisor before acting.