Year-End Tax Planning Checklist for Self-Employed & Small Business Owners (2026)
W-2 employees have maybe two levers at year-end: max their 401(k) and fund an FSA. Business owners have twelve — and several of them close permanently on December 31. A solo consultant earning $350,000 who waits until February to "think about taxes" has already left $30,000–$60,000 in deductions on the table.
This checklist covers every time-sensitive action available to sole proprietors, LLC owners, S-corp shareholders, and small-business owners with employees. December 31 is a hard wall for most of these.
Your Year-End Checklist
Check off each item as you review it. Items remaining count down at the bottom.
If you have a solo 401(k), your employee deferral election for 2026 must be made before December 31 — even if you fund it by April 15 of next year. No election by Dec 31 means you lose the employee deferral bucket entirely: up to $24,500 ($33,500 age 50–59; $35,750 age 60–63).1
The employer profit-sharing contribution (up to 25% of W-2 or 20% of net SE income) can still be made by your tax-filing deadline with extensions. But the employee side requires the prior-year election.
New solo 401(k) for 2026? You must adopt the plan by December 31, 2026 to make any 2026 contributions. Solo 401(k) rules and 2026 limits →
Cash balance plans stacked on top of a solo 401(k) can generate deductions of $100,000–$330,000 per year depending on age. But cash balance plans require actuarial certification, and contributions are typically due by the plan's funding deadline — usually December 31 of the plan year.
If you don't already have a cash balance plan and your income is above $200K, this is one of the highest-value calls you can make in Q4 with a CPA or financial advisor. At age 52 with $380K net income, a cash balance plan can add roughly $210,000 in annual deductions on top of a maxed solo 401(k). Cash balance plan guide with age-indexed contribution table →
S-corp owners pay FICA only on W-2 wages — not on distributions. The IRS requires "reasonable compensation," but there's often a range. Two legitimate reasons to adjust your salary before year-end:
- Too low? A salary under the IRS floor for your role risks reclassification. A year-end bonus paid through payroll can raise your documented compensation.
- QBI phase-out zone? If your income is near the QBI phase-out threshold ($201,775 single / $403,500 MFJ in 20262), a higher W-2 wage increases the W-2 wage limitation in the deduction formula — potentially recovering thousands in QBI benefit.
- Too high? If you took a large salary and 2026 income ended up lower than projected, you can adjust the year-end bonus down (not yet paid) to stay at the right ratio.
This adjustment must be reflected in your payroll processor before December 31 — no retroactive payroll adjustments after the fact. S-corp reasonable salary calculator → | S-corp payroll setup guide →
Section 199A gives most self-employed owners a 23% deduction on qualified business income — but it phases out for specified service trade or businesses (SSTBs: attorneys, consultants, financial advisors, health professionals) above $201,775 (single) or $403,500 (MFJ) in 2026.2
If you're in the phase-out range, every dollar of retirement contribution reduces your QBI income — which can increase your QBI deduction dollar-for-dollar. At the 37% marginal rate, recovering the QBI deduction effectively gives those retirement dollars a ~60% combined federal tax benefit.
This math closes December 31 for solo 401(k) deferral elections and for S-corp bonus payments. QBI deduction optimizer calculator →
In 2026 you can deduct 100% of qualifying business equipment in the year it's placed in service, thanks to OBBBA permanently restoring bonus depreciation for property acquired after January 19, 2025.3 Section 179 adds a separate $2,560,000 limit for direct expensing.4
Key: the equipment must be placed in service (operational and available for business use) before December 31 — a purchase order sitting on a loading dock doesn't qualify. For vehicles, this also means title in your name and business use logged.
Heavy SUVs (GVWR > 6,000 lbs, e.g. Ford Expedition, Chevy Suburban) get Section 179 up to $32,000 for the SUV cap, then 100% bonus on the rest. Light vehicles face §280F luxury caps ($12,300/$20,300 with bonus in Year 1). Section 179 & bonus depreciation calculator →
S-corp and partnership owners can rent their home to the business for up to 14 days per year under IRC §280A(g). The rental income is completely excluded from personal gross income; the business deducts it as an ordinary expense. At fair-market rental of $500/day, 14 days = $7,000 in tax-free income and a business deduction.
Requirement: the meeting or event must be a legitimate business purpose. If you haven't scheduled those 14 business meetings at your home yet for 2026, do it before December 31. Get a comparative market rent (Airbnb comparable), keep an agenda and attendance record. Augusta Rule guide and savings calculator →
S-corp owner-employees can reimburse home office, vehicle miles (72.5 cents/mile in 20265), phone, and professional expenses completely free of income tax and FICA — but only under a properly structured accountable plan. TCJA and OBBBA permanently eliminated the unreimbursed employee expense deduction for everyone else.
Year-end action: tally your YTD unreimbursed business expenses and submit them to your S-corp via an expense report before December 31. The corporation cuts a check; you receive tax-free income. A $16,000 annual reimbursement at 35% combined rate = $5,600 in annual tax savings. S-corp accountable plan setup guide →
Roth conversions are one of the few strategies that require you to execute the actual transaction before December 31 (unlike IRA contributions). Business owners in down years — or intentionally low-income years — have a unique window to convert traditional IRA or 401(k) dollars at a lower effective rate than they'll face in retirement.
How much to convert: fill your current bracket to the ceiling. At $160,000 of business income (single filer), the 22% bracket runs to $197,300 in 2026 — room for $37,300 of conversions at 22% before hitting 24%. After a business sale or in early retirement before RMDs begin, that window widens dramatically. Roth conversion calculator for business owners →
The Q4 estimated tax payment is due January 15, 2027. Unlike W-2 employees, self-employed owners must pay throughout the year or face underpayment penalties (IRC §6654). The two safe harbor methods for 2026:
- 90% of 2026 actual tax — calculate your full-year income and pay 90% across four installments.
- 100% of 2025 prior-year tax (110% if 2025 AGI exceeded $150,000) — pay this amount in equal quarterly installments regardless of 2026 income changes.
If you have a big Q4 — a large client payment, equipment sale, or business exit — the Q4 estimated payment needs to account for it. Missing the Jan 15 deadline doesn't cause a penalty per se, but underpayment of the full-year obligation does. Quarterly estimated tax calculator → | Estimated taxes guide →
If your LLC or C-corp earned $80,000–$200,000+ in 2026 and you're operating as a sole proprietor, you may save $5,000–$15,000 in FICA taxes annually by electing S-corp status for 2027. Form 2553 must be filed within 2 months and 15 days of the start of the tax year — which means March 15, 2027 for a calendar-year entity starting January 1, 2027.
Use Q4 to model the break-even math and get your CPA or advisor aligned before year-end. The S-corp election is not retroactive once you miss the window. LLC vs. S-corp break-even calculator →
HSA contributions for 2026 can be made up to April 15, 2027 — so this isn't a December 31 deadline. But contributing now rather than in April gives your HSA dollars roughly 4 extra months of investment growth, and ensures you're not scrambling to find cash in tax season. 2026 limits: $4,400 self-only / $8,750 family.6
S-corp owners (>2% shareholder): health insurance and HSA contributions must go through W-2 wages — no Section 125 plan. The HDHP premium gets Box 1 W-2 inclusion and then a Schedule 1 §162(l) deduction. Your HSA contribution is also above-the-line, not through an employer cafeteria plan. Verify this flow with your payroll processor before year-end. HSA for self-employed: limits, strategy, and the S-corp trap →
Pass-through entity tax (PTET) lets S-corps and partnerships deduct state income taxes at the entity level, bypassing the $40,400 SALT cap for high-income owners. Most states require an annual election — often by September 15 or December 31 of the tax year. Missing it means losing the deduction entirely for that year.
OBBBA raised the federal SALT cap to $40,400 but phases it out above $505K MAGI (back to $10K at $606K+), making PTET still essential for high earners in high-tax states. Verify your state's election deadline with your CPA now — several require the election before Q4 estimated payments. PTET guide and savings estimator →
The December 31 vs. April 15 split
One of the biggest year-end planning mistakes is assuming that because you can file your return until April 15 (or October 15 with extension), you can make all your tax moves that late. That's only true for a subset of contributions. Here's the actual split:
| Action | Hard Deadline | Notes |
|---|---|---|
| Solo 401(k) employee deferral election | December 31 | Must elect before year-end even if funding later |
| Solo 401(k) plan adoption (new plan) | December 31 | Can't create a plan after year-end for prior year |
| Cash balance plan contribution | Dec 31 (or plan deadline) | Actuarially determined; plan must already exist |
| Roth conversion | December 31 | Transaction must settle by year-end |
| S-corp salary/bonus payroll | December 31 | Must actually be paid through payroll |
| Section 179 / bonus depreciation | December 31 | Property must be placed in service |
| Augusta Rule meetings | December 31 | 14-day clock is per calendar year |
| Accountable plan reimbursements | December 31 (practical) | Technically 60 days post-expense, but sync with tax year |
| PTET election | State-specific (often Sept/Dec) | Varies by state; confirm with CPA |
| Q4 estimated tax payment | January 15, 2027 | Based on full-year liability |
| Solo 401(k) employer contribution (funding) | Tax filing deadline + extensions | Up to Oct 15 with extension for SE |
| SEP IRA contribution (funding) | Tax filing deadline + extensions | Up to Oct 15 with extension |
| IRA / Roth IRA contribution | April 15 | No extensions available for contributions |
| HSA contribution | April 15 | No extensions |
| S-corp election (Form 2553) | March 15 of new year | For calendar-year entity starting Jan 1 |
The year-end planning window by income level
$80K–$150K net business income
Priority actions: solo 401(k) deferral election, estimated tax check, S-corp election modeling for next year. At this income, the FICA savings from an S-corp election ($5,000–$12,000/year) often exceed the cost of setup and administration. The QBI deduction applies in full below the phase-out floor. If you don't have a solo 401(k), adopting one by December 31 is the highest-ROI action. Retirement plan selector calculator →
$150K–$300K net business income
Priority actions: solo 401(k) maxed ($24,500–$35,750 deferral + employer contribution), S-corp salary optimization, QBI deduction check (phase-out begins at $201,775 single / $403,500 MFJ), Roth conversion window, Augusta Rule and accountable plan expenses. This is the bracket where cash balance plans begin to generate meaningful deductions for owners age 45+. Cash balance plan guide →
$300K–$800K net business income
Priority actions: cash balance plan contribution, QBI phase-out mitigation (retirement contributions to recover the deduction), PTET election confirmation, Roth conversion or bracket analysis, year-end salary adjustment for QBI W-2 wage test, Augusta Rule + accountable plan finalization. At this income, each of the major items on this checklist can move $5,000–$30,000 in taxes. A coordinated approach across your CPA and financial advisor pays for itself several times over. How much does a fee-only advisor cost at this income level? →
Common year-end mistakes
- Waiting until January to "do year-end planning." Most of the highest-value actions require December 31 execution. Planning in January is post-mortem analysis, not planning.
- Forgetting the solo 401(k) deferral election. You can still fund the employer contribution in April, but the employee deferral — often $24,500–$35,750 — vanishes if not elected before Dec 31.
- Treating QBI as a fixed number. The QBI deduction is a moving target you can influence through retirement contributions and S-corp salary levels. Missing this interaction costs thousands.
- Skipping the PTET election deadline. Most business owners in high-tax states know about PTET in theory but miss the state-specific election deadline. The consequence is losing the deduction for the entire year.
- Not reconciling S-corp payroll before year-end. The IRS requires documentation of W-2 wages paid — not just declared — to support reasonable compensation and retirement plan deductions.
- Augusta Rule meetings undocumented. The exclusion is real and legal, but requires a contemporaneous record of business purpose, attendees, and fair-market rent. Don't use the strategy without the documentation.
When to call a specialist
Year-end planning has a short execution window and significant financial consequences. If your net business income is above $150,000 and you haven't reviewed this checklist with a fee-only financial advisor or CPA who understands self-employed planning, October–November is the right time to do it. By late December, some of these changes are logistically difficult to execute — payroll processors need lead time, brokerage transfers take days to settle.
A fee-only specialist who focuses on self-employed and small-business owners can model all twelve items simultaneously, identify which ones apply to your situation, and coordinate with your CPA on the tax return treatment. For owners earning $200K+, this engagement typically pays for itself in the first conversation. How to find a fee-only financial advisor for small business owners →
Sources
- Solo 401(k) 2026 deferral limits: $24,500 elective deferral, $8,000 catch-up ages 50–59, $11,250 super catch-up ages 60–63 — IRS Notice 2025-67 (IRS.gov, November 2025). Employee deferral election deadline: Dec 31 of plan year per IRC §402(g) and plan document requirements.
- Section 199A QBI deduction 2026 thresholds: $201,775 (single) / $403,500 (MFJ) phase-out range per OBBBA (Pub. L. 119-XX, July 2025), confirmed via Tax Foundation OBBBA analysis and IRS Form 8995-A instructions 2026 draft.
- 100% bonus depreciation permanently restored for qualified property placed in service after January 19, 2025 — One Big Beautiful Bill Act (OBBBA), Pub. L. 119-XX, July 2025; IRS Notice 2026-11 implementation guidance.
- Section 179 expensing limit: $2,560,000 for 2026, phase-out above $4,090,000 in property placed in service — section179.org 2026 update; cross-checked IRS Rev. Proc. 2025-32.
- Standard mileage rate 2026: 72.5 cents/mile for business use — IRS Notice 2026-10 (IRS.gov).
- HSA contribution limits 2026: $4,400 self-only / $8,750 family; HDHP minimum deductibles $1,700/$3,400; OOP maximums $8,500/$17,000 — IRS Rev. Proc. 2025-19.
Values verified May 2026. Tax law subject to change; confirm current-year limits with your CPA or financial advisor.