Year-End Tax Planning for Business Owners: 2026 Checklist

The biggest planning moves for business owners have hard December 31 deadlines — not April. A new retirement plan must be adopted before year-end. A Roth conversion must execute before the calendar turns. A heavy vehicle must be placed in service before December 31 to take bonus depreciation. Waiting until Q4 to start the conversation often means missing the best opportunities. This checklist organizes what to consider, and when, across the Q3–Q4 planning window.

1. Retirement Plan Moves (Largest Single Tax Lever)

Retirement plan contributions are typically the largest single deduction available to business owners. The caveat: some plans must exist before December 31 to count for the year.

Solo 401(k): Maximize Before Year-End

For the 2026 plan year, a Solo 401(k) lets you contribute up to $72,000 total — combining your employee salary deferral ($24,500, plus catch-up) with an employer profit-sharing contribution of up to 25% of W-2 wages (S-corp) or roughly 20% of net self-employment income (sole prop). The plan document must be adopted by December 31, 2026 for that year's contributions to count. Employee deferrals for S-corp owners must be elected and contributed from W-2 compensation paid by year-end; employer profit-sharing contributions can follow through the tax filing deadline with extension.

Use our Solo 401(k) Contribution Calculator to see your exact maximum, including how S-corp salary level trades off against total retirement space. See the full Solo 401(k) Guide for Roth and mega-backdoor Roth mechanics.

Cash Balance or Defined Benefit Plan: December 31 Adoption Deadline Is Hard

A cash balance plan or traditional defined benefit plan allows contributions far above what a 401(k) allows — from roughly $90,000–$110,000 at age 40 to $300,000–$340,000 at age 65 for the highest-contribution scenarios, stacked with a Solo 401(k). But unlike a SEP-IRA, the plan must be adopted by December 31 — no retroactive adoption. This is why the conversation needs to start in Q3, not November. Third-party actuarial design and plan documentation take time.

See our Cash Balance Plan Contribution Calculator and Cash Balance Plan Guide for age-based maximum tables and 401(k) stacking scenarios.

SEP-IRA: Flexible Deadline, But Lower Limits for S-Corp Owners

A SEP-IRA can be adopted through the tax return filing deadline including extensions (October 15, 2027 for most calendar-year filers). Contributions can be made at the same time. However, S-corp owners can only contribute 25% of W-2 wages — not total net income — which typically means the maximum is well below the Solo 401(k) total for the same income. If you're an S-corp owner with significant profit, the Solo 401(k) is almost always better. The SEP-IRA Guide and SEP-IRA Calculator show the detailed math.

Roth Conversion: Execute Before December 31

A Roth conversion — moving pre-tax IRA or 401(k) funds to a Roth account — must be completed by December 31 to count for the tax year. For business owners, the conversion amount is taxed as ordinary income, so timing matters: a year with unusually low income (major equipment purchases, high employee bonuses, large charitable deductions) can compress the effective rate. The strategy works best in years when you can fill up a lower bracket before pushing into 37%.

For 2026, the 32% bracket extends through $394,600 (single) / $526,600 (MFJ); the 35% bracket runs to $631,550 / $751,600. See the full Roth Conversion Guide for bracket-filling scenarios and the mega-backdoor Roth via Solo 401(k).

2. Entity and Compensation Moves

S-Corp Reasonable Compensation: Finalize Before December 31

If you're an S-corp owner, your W-2 salary for the year must be correct by year-end. You can issue a supplemental or corrected W-2 by January 31, but the actual payroll must run — you can't retroactively create W-2 wages after December 31. Under-paying yourself puts you at IRS audit risk (S-corp compensation is one of the IRS's top enforcement priorities). Over-paying costs unnecessary FICA. The goal is a documented, defensible salary that threads the needle.

Use our S-Corp vs LLC Tax Savings Calculator to model your optimal salary/distribution split, and read the Reasonable Compensation Guide for the IRS 9-factor framework and Watson v. Commissioner audit history.

PTET Election: Check Your State's Deadline

The pass-through entity tax (PTET) lets S-corps and partnerships pay state income tax at the entity level, generating a federal deduction that effectively bypasses the $40,400 SALT cap (2026, per OBBBA) for the business's state income taxes. Many states require the election to be made by a specific date — sometimes before year-end, sometimes by the extended return due date. Check your state's PTET deadline now; missing it means losing the deduction for the year. Use our PTET Savings Calculator to estimate the federal tax benefit.

S-Corp Distribution Timing

S-corp distributions are generally not subject to FICA, but they do affect your basis and your exposure to the additional Medicare tax (0.9% on wages above $200K/$250K MFJ) and the net investment income tax (3.8% on passive income above thresholds). Timing distributions around year-end can help manage both basis and bracket exposure. Owners planning large distributions in Q4 should track basis through October and coordinate with their CPA before December. See the S-Corp Shareholder Basis Guide and NIIT Guide.

3. Deduction Acceleration

Section 179 and Bonus Depreciation: Both Require December 31 Placed-In-Service

To deduct equipment, vehicles, or machinery in 2026, the property must be placed in service (operational, not just purchased or ordered) by December 31. There are two routes:

• Section 179: Deduct up to $2,560,000 of qualifying property immediately (2026 limit; phases out dollar-for-dollar above $4,090,000 in total asset spending). Applies to equipment, vehicles, off-the-shelf software, and certain building improvements.³
• Bonus depreciation: 100% first-year deduction on qualifying property placed in service after January 19, 2025 — permanently restored by OBBBA with no sunset. Applies to new and used property. No dollar ceiling. Bonus dep is typically more flexible than §179 (no taxable income limitation).

For heavy vehicles (over 6,000 lb GVWR — full-size pickups, SUVs), the combination of §179 (up to $30,500 for SUVs) and bonus depreciation can produce a very large year-1 deduction. The vehicle must be placed in service and used for business by December 31. See the Vehicle Deduction Guide for §280F luxury auto caps and S-corp accountable plan requirements.

For business owners who own commercial real estate, a cost segregation study can accelerate depreciation on components classified as 5-, 7-, or 15-year property (vs. the 39-year default for buildings), all eligible for bonus depreciation. See the Cost Segregation Guide.

Augusta Rule: Use All 14 Days Before December 31

Under §280A(g), an S-corp or C-corp owner can rent their personal residence to the entity for up to 14 days per year — and the rental income is tax-free to the owner (no deduction limitation because it's under the 14-day threshold), while the entity deducts the rental as a business expense. The 14-day limit is a hard calendar-year cap. Any unused days don't carry over. If you've only used 8 days, schedule additional board meetings, retreats, or business sessions before December 31. Documentation must be contemporaneous. See the Augusta Rule Guide for FMV requirements and audit red flags.

Home Office Documentation

If you claim the home office deduction, strengthen your documentation file before year-end: square footage measurements, photos of the space in exclusive business use, and a log of hours worked from the office. For S-corp owners, this deduction must run through an accountable plan reimbursement, not a personal deduction. The accountable plan must be in writing and pre-established — not created in December to backdate expenses.

4. QBI Deduction Optimization

The Section 199A QBI deduction allows up to 20% of qualified business income for pass-through owners, subject to limitations that phase in above $403,500 MFJ (2026). Key year-end moves:

• W-2 wages paid to employees — the W-2 wage limitation (50% of W-2 wages paid by the business) only counts wages paid by December 31. If you're above the QBI phaseout and employ staff, accelerating a December bonus improves both morale and your QBI calculation.
• SSTB status check — specified service trades or businesses (law, accounting, consulting, health, etc.) lose the QBI deduction entirely above the phaseout range. If your business is borderline, entity structure choices made now can affect your 2026 deduction.
• Income management — if you're near but below the phaseout ($403,500 MFJ), deferring S-corp distributions or accelerating deductible expenses can keep you inside the full-deduction zone.

Use the QBI Deduction Calculator to model your 2026 deduction under different income scenarios.

5. Charitable Giving

Donor-Advised Fund: Bunch Contributions Before December 31

A contribution to a donor-advised fund (DAF) is deductible in the year the contribution is made, even if you direct grants to charities over multiple years. This lets you bunch multiple years of charitable giving into a single high-deduction year (often a business exit year or high-income year), get the full itemized deduction now, and distribute the funds to charities over time. Contributions of appreciated business interests or stock avoid capital gains tax. Make DAF contributions before December 31 to count for 2026.

Qualified Charitable Distribution: For IRA Owners 70½+

If you're 70½ or older with a traditional IRA, a qualified charitable distribution (QCD) allows you to transfer up to $111,000 directly to a charity — satisfying your RMD obligation without the distribution counting as taxable income.⁴ QCDs must be made by December 31. They do not stack with a DAF contribution (DAF is not a qualifying charitable recipient for QCD purposes).

Annual Gifting

The 2026 annual gift exclusion is $19,000 per recipient. Gifts above this threshold count against your lifetime exemption ($15M per person, permanent under OBBBA). For business owners beginning a succession or family transfer strategy, annual gifting is a low-friction way to gradually transfer wealth. Gifts must be completed (check cleared or assets transferred) by December 31. See the Estate Planning Guide for FLP discount strategies and GRAT mechanics.

Year-End Planning Timeline