Your CPA calls you in December. They say: “We have some year-end moves to think about.” That call sounds helpful. Here’s the problem — by the time December arrives, most of the high-leverage moves are already off the table.

Year-end tax planning for Wisconsin small business owners isn’t December work. It’s September and October work. This post gives you five specific moves to make before December 31, what each one is worth in real dollars, and how long each one takes to execute.

The Short Answer: Five Year-End Tax Moves That Actually Move the Needle

The five most valuable year-end tax moves for Wisconsin small business owners are: (1) max out or open a retirement plan before the deadline, (2) time major equipment purchases to capture Section 179 or bonus depreciation, (3) review owner compensation if you’re an S-Corp, (4) accelerate deductible expenses into the current year if income is higher than expected, and (5) review your estimated tax payments before the January 15 deadline. Each is explained in detail below.

Move #1: Max Out or Open a Retirement Plan Before the Deadline

For Wisconsin business owners, retirement contributions are one of the cleanest legal tax deductions available. A Solo 401(k) lets you contribute up to $69,000 for 2024 (or $76,500 if you’re 50 or older). A SEP-IRA lets you contribute up to 25% of net self-employment income, capped at $69,000.

Here’s the timing that matters: to contribute to a Solo 401(k) for the current tax year, the plan must be established by December 31. You can make the actual contribution later — but if the plan doesn’t exist by year-end, you lose the option entirely. SEP-IRAs have more flexibility and can be opened as late as your tax filing deadline, including extensions.

What this is worth: A Wisconsin S-Corp owner pulling $150,000 in W-2 wages who maxes out a Solo 401(k) can reduce taxable income by $23,000 in employee contributions plus up to $46,000 more on the employer side, depending on how the business is structured. At a combined federal and state effective rate of 30%, that’s real money.

Related reading: Best Retirement Plans for Small Business Owners in 2026, IRS Publication 560 (Retirement Plans for Small Businesses)

Move #2: Time Equipment Purchases for Section 179 or Bonus Depreciation

If your business needs equipment — machinery, vehicles, computers, tools — buying before December 31 lets you deduct the full cost in the current year instead of depreciating it over five to seven years.

The 2025 tax year is an unusually good one for this move. The One Big Beautiful Bill Act, signed into law on July 4, 2025, permanently doubled the Section 179 deduction limit to $2,500,000 for tax years beginning in 2025, with a phase-out threshold of $4,000,000. That’s a significant jump from the prior limit of $1,250,000. And 100% bonus depreciation has been restored and made permanent for qualified property placed in service after January 19, 2025 — after several years of phase-down, that’s back to full first-year write-off.

The catch is the same as always: the purchase must be placed in service — actually used in your business — before December 31. Ordering equipment isn’t enough. The equipment has to be in operation.

What this is worth: A $50,000 equipment purchase under Section 179 reduces your taxable income by the full $50,000 in year one. At a 25% effective tax rate, that’s a $12,500 tax reduction versus spreading the deduction over seven years. For larger purchases, the math gets even more compelling this year given the expanded limits.

Note: Wisconsin has its own conformity rules on bonus depreciation that don’t always match federal treatment. Your tax advisor should confirm the Wisconsin-specific treatment for your situation before you count on the full deduction at the state level.

Move #3: Review Owner Compensation if You’re an S-Corp

S-Corp owners pay themselves a reasonable W-2 salary and can take additional income as distributions. Distributions are not subject to self-employment tax. The legal requirement is that your W-2 salary reflects reasonable compensation for the services you provide to the business.

Year-end is the right time to look at where you are. If your salary has been set conservatively and the business had a strong year, there may be room to review compensation — either adjusting the W-2 before year-end or evaluating whether your current structure still makes sense.

What this is worth: Self-employment tax is 15.3% on the first $168,600 in income (2024) and 2.9% above that. For an S-Corp owner earning $200,000, getting the salary-to-distribution ratio right can be worth several thousand dollars annually.

This is a credentialed-advisor discussion, not a DIY move. But it’s worth having the conversation before the W-2 is finalized.

Move #4: Accelerate Deductible Expenses Into the Current Year

If this year’s income is running higher than expected — and higher than you anticipate next year will be — it makes sense to accelerate deductible business expenses into the current year. Prepay business insurance premiums. Pay Q1 professional fees now. Order supplies you’ll need in January. Renew software subscriptions before year-end.

The limit: you can generally deduct prepaid expenses only if the benefit period doesn’t extend beyond 12 months past the prepayment date (the “12-month rule”). So prepaying January through March expenses in December is clean. Prepaying a full year of something in December gets more nuanced.

What this is worth: For a business owner in the 24% federal bracket with $10,000 in expenses that can be shifted from next year to this year, that’s $2,400 in tax savings — the exact same deduction, just pulled forward.

Move #5: Review Your Q4 Estimated Tax Payment Before January 15

The final estimated tax payment for 2025 is due January 15, 2026. Before that deadline, review where you actually landed for the year versus what you’ve paid in through prior quarters.

Underpay by too much and you’ll owe a penalty. Overpay and you’re giving the IRS an interest-free loan until you get your refund. Either way, the Q4 payment is your last chance to calibrate.

If your business had a significantly better or worse year than expected, your estimated payments may be materially off. Pull the numbers with your advisor in October or November — not the second week of January.

Related reading: Why Small Business Owners Get Surprise Tax Bills 

What This Means for You

These five moves are worth real money for Wisconsin small business owners with $500K to $5M in revenue. But none of them happen automatically, and most require setup time, making November and December too late.

The owners who come out ahead every year aren’t smarter or luckier. They have an advisor who’s looking at their numbers in September, not December.

Ready to Have This Conversation Before Q4?

We work with small businesses in Wisconsin and Illinois year-round — not just at tax time. If you want to know which of these five moves applies to your business this year, the place to start is our pricing calculator or schedule a conversation with our team.

This article is provided for general informational purposes only and does not constitute tax, legal, accounting, or financial advice. Every business situation is different. Before acting on anything you read here, please consult with a qualified advisor — including, we hope, us. Reach out to Accounting Freedom for guidance specific to your situation.

About the Author

Frank Fiore, CPA is the Visionary of Accounting Freedom and Payroll Freedom, serving small business owners in Mundelein, Illinois, and Grafton, Wisconsin, since 1981. In over 40 years of practice, Frank has worked with Wisconsin and Illinois business owners across construction, medical, restaurants, family-owned businesses, and more. He’s known for telling clients what other CPAs won’t say out loud — including when the answer isn’t what they want to hear.