The year-end tax strategies that save the most money are the ones with setup requirements, filing deadlines, or paperwork that cannot be compressed into the last two weeks of December. Retirement plan design, owner compensation changes, equipment placed in service, charitable transfers of appreciated assets, and corrections to withholding all need lead time. Start them in October and most are still available to you. Wait until late December and most are gone, leaving only the small moves that rarely change an outcome.
By the time most owners and high earners sit down to talk about taxes, the calendar has already made the decision for them. The conversation happens in January, the number is what it is, and the only remaining question is how to pay it. The Harness Advisory Platform exists to move that conversation forward by three months, because October is when year-end tax strategies are still choices rather than history.
By October you have three quarters of real results. That is enough data to build a credible projection and still enough runway to act on it. December gives you better data and almost no time, which is the worst possible trade.
Your business is your most important investment, and the tax cost attached to it is one of the largest recurring drags on its value. A five figure difference in tax is a five figure difference in retained earnings, in what you can reinvest, and eventually in what a buyer sees when they look at your numbers. Treating that as a filing-season problem rather than an operating decision is how owners quietly leave money in the same place every year.
The AICPA has consistently framed tax planning as a year-round advisory function rather than a compliance season activity, and the reason is structural. Most of the code's meaningful elections require something to exist, be adopted, be funded, or be placed in service before a date. None of those things happen on a phone call on December 28.
Any CPA firm can record history. As your tax advisory partner, we help you build a future, and the difference shows up most clearly in the fourth quarter.
These are the five that most often get missed, and the reason they get missed is almost always timing rather than cost.
Yes, and several of them fall well before year-end. A new safe harbor 401(k) has to be in place for a minimum plan year of three months under IRS rules, which makes October 1 the practical cutoff for a calendar-year plan, and the required employee notice has to go out roughly 30 days ahead of the effective date. Miss that window and the earliest realistic start is the following January.
Defined benefit and cash balance plans take longer still. They require an actuary, a plan document, and a funding analysis, and that process realistically runs six to ten weeks. For owners with high, stable profit and few employees, these plans often allow far larger deductible contributions than a 401(k) alone, which is exactly why the design work cannot be rushed.
There is a partial safety net. Later legislation allows an employer to adopt a qualified plan after year-end, up to the tax filing deadline including extensions, and SECURE 2.0 extended limited deferral flexibility to sole proprietors in a first plan year. What retroactive adoption generally does not give you is the ability to make employee elective deferrals for a year that has already closed, and deferrals are usually the larger number. Owners hear that a plan can be set up later and assume the whole contribution is preserved. Often it is not.
SECURE 2.0 also expanded the small employer start-up credit, covering up to 100 percent of qualifying start-up costs for employers with 50 or fewer employees, capped at $5,000 per year for the first three years. That materially changes the math on whether a plan is affordable, and it is worth running before you decide against one.
Usually yes, but only if you move now. S corporation owners have to take reasonable compensation through actual payroll, and payroll runs on a processing calendar that does not care about your intentions. Most providers need instructions well before the final December run, and a true-up that gets missed cannot be fixed by writing yourself a check in January.
The same applies to shareholder health insurance, accountable plan reimbursements, and accrued bonuses. Each one has a documentation step, and each one is routinely reconstructed after the fact, which is where the risk comes from. Getting owner compensation right also affects your qualified business income position and your retirement plan contribution ceiling, so it is rarely a standalone decision.
The rule that matters is placed in service, not ordered and not paid for. An asset delivered on January 3 does nothing for the current year no matter when the invoice was signed. Vehicles, specialty equipment, and anything with a manufacturing lead time need to be ordered in October or early November to clear that bar.
Expensing rules under Section 179 and bonus depreciation have changed repeatedly in recent years, and current-year treatment should be confirmed before you commit capital. Under the One Big Beautiful Bill Act, the Section 179 deduction limit for 2026 is $2.56 million, with the phase-out beginning at $4.09 million of equipment purchases, and 100 percent bonus depreciation was made permanent for qualifying property. The larger point holds regardless of the percentage. Buying equipment you do not need in order to reduce tax is a poor investment decision wearing a tax costume. Accelerating a purchase you were already going to make is a good one.
Longer than almost anyone expects. Opening a donor-advised fund account, initiating a transfer from a brokerage, and getting the securities delivered can take two to four weeks, and mutual fund positions often move more slowly than individual stocks. Custodians publish year-end cutoff dates in November, and gifts that settle on January 2 count for the following year.
The strategy itself is straightforward. Giving long-term appreciated securities directly to a qualified charity generally avoids the capital gains tax you would owe on a sale while allowing a deduction at fair market value, subject to AGI limits. Bunching several years of giving into one year can push you over the standard deduction threshold in a year when it is worth the most. Both work. Neither works on December 30.
No, and this is the one strategy that actually gets easier late in the year. IRS Publication 505 sets out the safe harbors that protect you from an underpayment penalty: generally paying in 90 percent of the current year's tax, or 100 percent of the prior year's tax, rising to 110 percent if your prior-year adjusted gross income exceeded $150,000.
The useful mechanic is that federal income tax withheld from wages is generally treated as paid evenly across the year regardless of when it was actually withheld. That means increasing Q4 withholding through payroll can cure a shortfall created in the spring, something an additional estimated payment in January cannot do as cleanly. For owners who take a W-2 and for high earners with a working spouse, this is often the single most efficient late-year correction available.
You can reasonably handle the following on your own:
The items that benefit from a strategic advisor are the ones where the pieces interact. Retirement plan design affects owner compensation, which affects qualified business income, which affects your projection, which affects whether the equipment purchase makes sense at all. Optimizing any one of those in isolation frequently makes another worse. That is the work, and it is why the conversation is worth having with someone who sees the whole picture.
This is a fictional example created to illustrate how Harness Advisory would approach this situation. It is not a real client.
Patrick owns a specialty engineering consulting firm in Missouri with about $2.1 million in revenue, nine employees, and an S corporation structure. His profit is running roughly 40 percent ahead of last year after landing two multi-year contracts in the spring. His plan for the year was to look at it in December and maybe buy a truck.
Harness Advisory would start with an October projection rather than a strategy list, because the projection determines which strategies are worth doing at all. With that number in hand, our advisory team would walk through the sequence. The safe harbor 401(k) window for the current year has already closed, so we would design it for a January 1 start and run the SECURE 2.0 start-up credit analysis now rather than revisiting it next fall. We would model a profit sharing contribution against the existing plan for the current year, since employer contributions retain more flexibility than deferrals.
We would then review his reasonable compensation against the increased profit and schedule any true-up with his payroll provider before the December cutoff, not after it. The truck would be evaluated on whether the business actually needs it and whether it can be delivered and placed in service before December 31, with the tax benefit treated as a secondary factor. Finally, we would raise his Q4 withholding to land inside the safe harbor rather than leaving a balance due in April.
None of those moves are exotic. All of them require October.
If parts of this sound like your own year, the timing problem is the part worth acting on first.
Harness Advisory is a national tax advisory and business advisory platform, and the fourth quarter is where that distinction becomes concrete. A compliance-first firm reports what happened. Our advisory team works from a projection built before the year closes, so the decisions are still yours to make.
That means an advisory cadence with scheduled planning checkpoints, decision-ready books that support real operating decisions rather than just a return, and an integrated view that connects tax, compensation, retirement design, and cash flow into one plan. Clients tend to describe the relationship as closer to a board member than a bookkeeper, because the questions we raise are the ones that affect enterprise value, not just this year's refund.
It is a structured, educational discussion, not a line-by-line review of your books. We look at where the year is landing, which decisions are still open, and which deadlines are close enough to force a sequence. You leave with a clear view of what is worth doing before December 31, what should be set up for next year instead, and whether deeper advisory support makes sense for your situation. There is no obligation beyond the meeting.
| The strategies that matter most in December are the ones you start in October. If you want to know which ones are still open for your business or household this year, schedule a fall planning conversation with Harness Advisory. |
Book your meeting: https://outlook.office.com/book/[email protected]/
Start in October at the latest. By then you have three quarters of actual results, which is enough to build an accurate projection, and you still have time to act on deadlines that fall before December 31. Waiting until December limits you to the handful of strategies that require no setup, no funding, and no third-party processing.
Retirement plan design takes the longest, particularly safe harbor 401(k) plans and cash balance plans. A new safe harbor 401(k) must generally be in place three months before year-end under IRS rules, and cash balance plans require actuarial work that can run six to ten weeks. Charitable transfers of appreciated securities and equipment with manufacturing lead times are close behind.
It depends on the plan type and on whether you need employee deferrals. Later legislation allows some employer plans to be adopted after year-end, up to the tax filing deadline including extensions, but that generally does not let you make elective deferrals retroactively for a closed year. Since deferrals are usually the larger contribution, this is worth confirming rather than assuming.
Some options remain, but the list is short. Increasing Q4 payroll withholding is the most useful one, because IRS rules generally treat wage withholding as paid evenly across the year, which can cure an underpayment created months earlier. Beyond that, most December moves are small relative to what was available in October.
Only if the asset is placed in service by December 31, meaning delivered and ready for use, not simply ordered or paid for. Current-year expensing treatment under Section 179 and bonus depreciation should be confirmed before committing capital. Buying equipment you do not need in order to reduce tax destroys more value than it saves.
Talk with an advisor when the decisions start interacting, which for most owners is the point where retirement plan design, owner compensation, and capital purchases are all on the table at once. Optimizing one of those in isolation often makes another worse. Harness Advisory works through the full sequence with business owners and high earners nationally, and a fall planning conversation is a low-pressure way to see what is still open this year.
