Key Takeaways

• Not every year-end deadline is actually urgent. Charitable gifts, Roth conversions, annual exclusion gifts, securities sales, and 2027 deferred compensation elections require action by December 31, but many retirement plan contributions can be funded well into next year.
  
  

• The 2026 charitable rules changed the math for itemizers — and introduced a new deduction for non-itemizers. For itemizers, a new 0.5% of AGI floor applies before any charitable deduction counts, and a separate limitation trims the benefit further for taxpayers in the top bracket. For non-itemizers, a new above-the-line deduction of up to $1,000 (single) or $2,000 (married filing jointly) is now available — but only for cash gifts to qualified public charities, not for stock donations or contributions to donor-advised funds.
  
  

• State tax rules can override the federal answer. Wash sale disallowance, bonus depreciation conformity, and pass-through entity tax elections vary widely by state, so a federally sound strategy can produce a different — sometimes worse — result depending on where you're taxed.

Most of what feels urgent about taxes in December is a habit, not a deadline. Business owners walk into the fourth quarter assuming everything has to close out by December 31, and that assumption is what turns a manageable review into a scramble — often producing a worse decision than the one made calmly a few months later.

This matters most for founders, business owners, and executives whose income doesn't arrive on a single, predictable schedule: a concentrated equity position, a pending sale, S corporation payroll, deferred compensation, or a charitable plan layered on top of it all. For this group, a handful of year-end moves are genuinely irreversible after December 31, while several others that feel urgent are not deadlines at all.

2026 raises the stakes on getting the distinction right. New charitable deduction rules — a floor for itemizers and a separate deduction for non-itemizers — change what a gift is actually worth and how it should be structured. A mandatory Roth catch-up rule changes how certain payroll deferrals must be coded. The return of the ACA subsidy cliff means a single poorly timed sale can cost far more than the tax on the gain itself. State tax rules add another layer, since several federal strategies — bonus depreciation, wash sale disallowance, pass-through entity tax elections — produce a different answer depending on where a business and its owners are taxed.

What follows is a framework for sorting real December 31 deadlines from decisions that have more room than they appear to, along with the specific 2026 figures that changed the math.

Why Year-End Tax Planning Works Differently for Business Owners

For a W-2 employee, most of the tax year is already locked in by December: withholding is set, contribution limits are fixed by payroll, and there's little left to move. For a founder or business owner, the picture is different because so many income items are still elective in the fourth quarter — owner wages processed through payroll, the timing of a securities sale, the size of a Roth conversion, and whether a charitable gift lands this year or next.

Every one of those decisions moves the same adjusted gross income (AGI) or modified adjusted gross income (MAGI) figure, and in 2026 more thresholds are keyed to that figure than in prior years: the new charitable deduction floor, the itemized deduction limitation for top-bracket taxpayers, the SALT cap phase-down, Medicare's IRMAA surcharge, and the ACA premium subsidy cliff.

That's why year-end planning for this audience isn't a checklist executed line by line — it's a single full-year income projection that determines which moves are worth making and in what order. A charitable gift, a stock sale, and a Roth conversion sized independently can each look reasonable and still combine to push a household across a threshold that costs more than any one of them saved.

When Do Year-End Tax Moves Actually Pay Off?

Year-end moves earn their complexity when a household can see, with reasonable confidence, that this year's income picture is meaningfully different from next year's — or when a rule change makes the timing of an otherwise-planned action worth adjusting.

Charitable Bunching Ahead of a Known Floor

Combining two or more years of planned giving into a single tax year works best for donors who itemize, give consistently, and hold appreciated securities or a donor-advised fund to make the timing practical. Because 2026 introduced a floor that has to be cleared before any charitable deduction counts, giving the same total amount in fewer, larger years reduces how many times that floor erodes the deduction.

Roth Conversions in a Genuinely Low-Income Year

A conversion makes the most sense in a year when income is unusually low relative to a normal year — between jobs, in an early-retirement gap before Social Security or pension income starts, or in a year with an unusually large deduction. Converting into unused room in a lower bracket, without crossing an IRMAA tier or the ACA subsidy threshold, is the scenario that consistently produces a good result.

Deferred Compensation Elections Before a Known Income Jump

For an executive or founder who knows 2027 income will be meaningfully higher — a closing bonus, an equity vesting event, a planned liquidity event — electing to defer 2027 compensation before it's earned can shift income into years with more favorable brackets. Because the election must be made before the deferred year begins, this is one of the few moves that requires action based on a forecast rather than a known result.

When Should You Skip Year-End Tax Moves Entirely?

Some of the most common December moves destroy more value than they create.

• A Roth conversion sized for a high-income year — especially one that pushes income across an IRMAA tier or the ACA subsidy cliff. Crossing that threshold removes the entire subsidy, not a portion of it.
  
  

• Purchasing equipment solely to capture a deduction. A deduction lowers the after-tax cost of a purchase; it doesn't turn an unnecessary purchase into a good one. In states that don't conform to federal bonus depreciation, the first-year benefit is also smaller than it appears.
  
  

• Bunching charitable gifts in a year the household won't otherwise itemize — the floor and the deduction only matter for itemizers in the first place. If you're not itemizing, the bunching strategy doesn't apply; you'd use the separate non-itemizer deduction instead (with its cash-only restriction).
  
  

• Treating a solo 401(k) or SEP deadline as a hard December cutoff, when the actual rule allows funding — and sometimes plan adoption — well into the following year's filing season.
  
  

• Ignoring wash sale exposure across household accounts, including a spouse's IRA, when harvesting a loss. The federal disallowance window runs 61 days, not 30.
  
  

The common thread: year-end pressure pushes people toward moves that look identical to a good strategy but are missing the one condition that makes them worthwhile — genuinely different income years, an existing itemizing pattern, or an economic reason for the transaction beyond the tax result.

Bunching Charitable Gifts vs. Giving Annually: Which Wins Under the New Floor?

Two structurally different approaches to the same total giving amount produce different outcomes under the 2026 floor.

Requires Action by December 31 vs. Can Extend Into Next Year

Charitable Bunching vs. Giving Annually

Both approaches require reevaluating standard-deduction thresholds each year, and neither changes state-level charitable treatment, which does not automatically track the federal itemized deduction in every state. The dollar comparison further below shows why bunching produces a larger two-year deduction even though the household gives the same total amount either way.

One important structural point for business owners: the new non-itemizer deduction ($1,000 single / $2,000 MFJ) is a separate provision from the itemizer rules above. It is for cash gifts only — appreciated stock donations and contributions to donor-advised funds do not qualify. A business owner who routinely donates stock to a DAF should not assume this new deduction is available for those gifts; it is not. Only direct cash contributions to qualifying public charities count.

The Most Misunderstood Part of Year-End Planning: State Tax Conformity

Federal rule changes get the attention, but state-level nonconformity is where projected savings quietly disappear.

Bonus Depreciation Doesn't Always Follow Section 179

For 2026, the federal Section 179 limit is $2.56 million, phasing out once qualifying property placed in service exceeds $4.09 million, and 100% bonus depreciation applies to qualifying property acquired and placed in service after January 19, 2025. Some states have adopted the federal Section 179 limit but still disallow bonus depreciation for state income tax purposes — meaning an asset fully expensed federally may still need to be depreciated over its useful life on the state return, turning what looks like a permanent deduction into a timing difference.

Wash Sale Rules Aren't Universal

The federal wash sale rule disallows a loss when a substantially identical security is purchased within a 61-day window around the sale, reaching a spouse's account or an IRA. Not every state applies the same rule, and some states provide no loss carryforward at all — meaning a loss disallowed (or simply unused) can produce zero state benefit, now or later, a very different outcome from the federal treatment.

Pass-Through Entity Tax Elections Aren't Available Everywhere

Many states with an income tax now offer an elective pass-through entity tax that converts an owner's state income tax into an entity-level federal deduction, working around the SALT cap. A small number of states with a personal income tax still don't offer this election at all, which means owners there need to model the federal SALT limitation directly rather than assuming a workaround exists.

A Founder's Year-End Numbers: What Bunching $40,000 in Gifts Actually Saves

Consider a married couple — one a 54-year-old business founder — with $1 million of adjusted gross income in both 2026 and 2027, who give $20,000 per year to charity and itemize in both years. Ignoring other limitations, the new 0.5% AGI floor is $5,000 in each year.

The same $40,000 of total giving produces $5,000 more of potentially deductible contributions, because the 0.5% floor is applied once instead of twice. Assuming an illustrative 37% marginal federal rate, that extra $5,000 of deductions is worth roughly $1,850 in reduced federal tax over the two years — before accounting for the itemized deduction limitation that can also apply at this income level.

Is Aggressive Year-End Tax Planning Right for You?

This kind of coordinated, deadline-driven planning delivers the most value to households with more than one moving piece landing in the same tax year: a founder finalizing S corporation payroll, an executive with equity vesting alongside a charitable plan, a business owner weighing a Roth conversion against a pending sale, or anyone who knows 2027 income will jump enough to make a deferred compensation election worth considering now.

For someone with a single, stable W-2 income, the standard deduction, and no equity or business ownership, most of this list simply doesn't apply — a much shorter, simpler review is appropriate. The complexity is warranted specifically because these income levers interact, and because 2026's new thresholds punish moves made in isolation from one another.

Frequently Asked Questions

What tax moves absolutely must be completed by December 31, 2026?

Charitable gifts intended for a 2026 deduction, Roth conversions, annual exclusion gifts, securities sales meant to realize a 2026 gain or loss, S corporation owner payroll adjustments, 2027 deferred compensation elections under Section 409A, and property that must be placed in service for a 2026 deduction. Retirement plan funding often has more flexibility than these items.

How did the charitable deduction change for 2026?

Two separate sets of rules apply depending on whether you itemize.

For itemizers: Charitable deductions are now subject to a 0.5% of AGI floor, meaning only contributions exceeding 0.5% of AGI are deductible. Taxpayers in the top bracket also face a limitation — deductions are reduced by 2/37 (approximately 5.4%) of the lesser of total itemized deductions or the amount of taxable income exceeding the 37% bracket threshold ($640,600 for single filers and heads of household; $768,700 for married filing jointly in 2026). The practical effect is that itemized deductions for 37% bracket taxpayers deliver a 35% tax benefit rather than 37%.

For non-itemizers: A new above-the-line deduction of up to $1,000 (single) or $2,000 (married filing jointly) is now available for qualifying cash contributions to public charities — even when taking the standard deduction. This deduction has important restrictions: it applies only to cash gifts (not appreciated stock), and contributions to donor-advised fund sponsors and most private foundations do not qualify. The limits are not indexed for inflation.

These two provisions are mutually exclusive in any given tax year — a taxpayer either itemizes (with the 0.5% floor and 5.4% limitation applying) or takes the standard deduction plus the new above-the-line deduction.

Can I still open or fund a retirement plan after December 31?

In many cases, yes. Employer profit-sharing and matching contributions can often be funded — and still count for the prior year — up to the extended business return deadline, and SEP plans can generally be established and funded on that same timeline. Certain sole proprietors also get a special first-year solo 401(k) rule allowing plan adoption after year-end. Employee elective deferrals are the exception; those generally must be elected before the related compensation is paid.

What happens if I don't watch the Roth catch-up rule for 2026?

2026 is the first year the mandatory Roth catch-up rule is active. If an employee had more than $150,000 in prior-year Social Security wages from the plan sponsor, 2026 catch-up contributions generally must be coded Roth rather than pre-tax. This is far easier to fix before the final payroll run than after a W-2 is issued, and self-employed owners with no W-2 wages from that employer generally don't trigger it based on business income alone.

Why would a Roth conversion backfire even though it seems tax-efficient?

A conversion adds to income in the conversion year, and if that pushes MAGI over an IRMAA tier — felt two years later — or over the ACA subsidy cliff at 400% of the federal poverty line, the cost can dwarf the tax on the converted amount. These are cliffs, not gradual phase-ins. Converting only within the room below the next threshold, in a genuinely low-income year, is what separates a good conversion from an expensive one.

Is buying equipment before year-end actually worth the deduction?

Only if it's a purchase the business needs anyway. A deduction reduces the after-tax cost of an asset — it doesn't create value out of an unnecessary purchase. Property also has to be placed in service, meaning ready and available for use, not just ordered or invoiced, to count for a given tax year, and in states that don't conform to federal bonus depreciation, the real first-year benefit is smaller than the federal number implies.

Does my state tax a Roth conversion the same way the federal government does?

It depends on your specific state's rules for retirement income. Many states with an income tax don't tax a traditional-to-Roth conversion as separate income when the funds move directly into the Roth account, though amounts withheld to pay the tax — rather than deposited — can be taxable there. Confirm the treatment for your state before finalizing conversion size, since the answer changes the total cost.

Can I donate stock to a donor-advised fund and claim the new non-itemizer deduction?

No. The new above-the-line deduction for non-itemizers applies only to cash gifts to qualifying public charities — contributions of appreciated stock and contributions to donor-advised fund sponsors are both explicitly excluded. A business owner who uses a DAF as their primary charitable vehicle cannot use that DAF funding to claim the non-itemizer deduction. The DAF strategy remains valuable for itemizers, particularly for bunching and for donating appreciated stock to avoid capital gains — but it is a separate strategy from the non-itemizer deduction.

What's the biggest mistake people make with year-end tax planning?

Sizing each move — a charitable gift, a stock sale, a conversion — independently instead of against one full-year income projection. Several 2026 thresholds (the charitable floor, IRMAA, the ACA cliff, the SALT phase-down) are all keyed to the same AGI or MAGI figure, so a set of individually reasonable decisions can combine to push a household over a line that costs more than any single move saved.

Where This Leaves You

This kind of planning is most valuable for founders, business owners, and executives with more than one moving piece in the same tax year — a pending sale, S corporation payroll, a charitable plan, or income about to jump in 2027. The moves that matter most are the ones with a hard December 31 deadline, and the moves that do the most damage are the ones made in isolation from everything else on the return. Endeavor Advisors builds the full-year income projection first, then sequences the charitable, Roth, SALT, and compensation decisions against it so nothing gets rushed and nothing real gets missed. If year-end is approaching and your income picture has more moving parts than usual, our contact page is the place to start that conversation.