2026 Year-End Tax Planning: Deadlines and Checklist
What has to happen by December 31, what can wait for your return, and where to go next if you're a physician, real estate investor, business owner, or equity comp holder.
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8 Strategic Sections
Real Dollar Examples
2026 year-end deadlines: December 31 vs the filing deadline
Calendar-year filers: individuals and sole proprietors file by April 15, 2027, or October 15, 2027 on extension. S corps and partnerships file by March 15, 2027, or September 15, 2027 on extension.
| Move | By December 31, 2026 | By the filing deadline |
|---|---|---|
| 401(k) deferrals | Through your final 2026 paycheck, up to $24,500 ($32,500 at age 50 or older). | Nothing left to do. |
| Solo 401(k) | Elect your employee deferral. S corp owners run it through final payroll. | Employer contributions by the return due date, with extensions. A sole proprietor with no employees can adopt a first plan by April 15, 2027, no extension. |
| SEP-IRA | Nothing required. | Set up and fund by the return due date, with extensions. |
| Cash balance plan | Nothing required, but the actuary needs weeks, so start now. | Adopt and generally fund by the return due date, with extensions. |
| Backdoor Roth | Clear pre-tax IRA balances. Form 8606 uses your December 31 value. | Make the 2026 IRA contribution by April 15, 2027, no extension. |
| Roth conversion | Finish the conversion. It cannot be undone. | Nothing left to do. Report it on Form 8606. |
| HSA | Payroll contributions through your final paycheck. | Direct contributions by April 15, 2027. |
| S corp salary | Run owner wages and 2% shareholder health insurance through December payroll. | Nothing left to do. It cannot be fixed after year-end. |
| S corp election for 2027 | Can be filed any time in 2026. | Form 2553 by March 15, 2027. |
| Equipment, vehicles, and rentals | Placed in service, meaning ready and available for use. An order or deposit is not enough. | Claim Section 179 or bonus depreciation on the return. |
| Cost segregation | Property placed in service. | Finish the study before you file. |
| Short-term rental hours | Log material participation inside 2026. | Nothing left to do. January hours count toward 2027. |
| Augusta rule | Hold the meetings and have the business pay the rent. | Report the rent deduction on the business return. |
| Tax-loss harvesting | Trade by December 31. The trade date controls, and the wash sale window runs 30 days each way. | Nothing left to do. |
| Charitable gifts | Delivered to the charity or fund. Stock transfers take days. | Nothing left to do. |
| ISOs and RSUs | Model AMT before exercising, decide on any same-year sale, and cover RSU withholding gaps. | Pay any balance due with the return. |
| Fourth-quarter estimate | Nothing required. | January 15, 2027, ahead of the filing deadline. |
Federal rules for tax year 2026. State deadlines and your facts can change the answer. Educational, not individualized tax advice.
Year-end tax planning for physicians
W-2, 1099, and locum income often land on one return, so deferrals, retirement plans, and estimates have to work together.
- Cash balance plans →Start the plan design now if you want a 2026 deduction. The actuary needs weeks.
- Backdoor Roth pro rata rule →Roll pre-tax IRAs into your 401(k) so the money is out by December 31.
- Solo 401(k) calculator →Size your 2026 contribution so you know the cash you need.
- Physician year-end checklist →Deferrals, backdoor Roth, and Q4 estimates for W-2, 1099, and locum income.
- CPA for physicians →How we plan for employed physicians, locums, and mixed income.
Year-end tax planning for real estate investors
Most real estate deadlines turn on dates and records: when the property was ready to rent and what your hours log shows.
- Cost segregation →See whether a study pays off. The property has to be placed in service by December 31.
- Short-term rental loophole →Log your participation hours inside 2026. January hours count toward 2027.
- Real estate investor year-end checklist →Placed-in-service dates, cost segregation, hours, and sale timing.
- CPA for real estate investors →How we coordinate rentals, depreciation, and your wider tax picture.
Year-end tax planning for business owners
Payroll closes on December 31. Owner pay, purchases, and home rentals all have to be done in the year they count.
- S corp reasonable salary →Set owner wages and 2% shareholder health insurance through December payroll.
- Augusta rule →Hold the meetings in 2026 and have the business pay the rent by December 31.
- Vehicles over 6,000 lbs →Take delivery and start using the vehicle by December 31, not just order it.
- S corp year-end checklist →Final payroll, salary, and distributions.
- Year-end planning for small business owners →Lock in payroll, equipment, and retirement decisions before December 31.
- Small business CPA →Monthly accounting, returns, and planning for owners.
- Tax planning services →What a written plan includes and how the engagement works.
Year-end tax planning for equity compensation
Withholding and AMT are the two year-end surprises. Both are easier to fix before the last paycheck.
- Double-trigger RSUs →Plan withholding before an IPO or sale settles years of vesting at once.
- ISO vs RSU →Model the AMT before you exercise ISOs and hold the shares past December 31.
- RSU tax calculator →Check the gap between 22% withholding and your real bracket while you can still fix it.
- Equity compensation year-end checklist →RSUs, ISOs, and ESPP shares.
- High-income W-2 year-end checklist →Retirement accounts, HSA, and withholding.
- Tax strategies for high income earners →15 moves, each with a December 31 action.
What changed for 2026? See the 2026 tax law changes hub before you act on any year-end move.
October Tax Planning Priorities
Critical decisions this month set the tone for Q4
October is your gateway to tax optimization. With 92 days remaining in the tax year, you have sufficient time to implement major strategies. Many year-end moves, from retirement plan setup to equipment orders with delivery lead times, need weeks of runway, so October decisions directly affect your December 31st year-end position.
The three critical October moves are: (1) estimating final Q4 income, (2) reviewing estimated tax payments to avoid penalties, and (3) planning for expense acceleration or income deferral based on projected taxable income.
October Checklist:
- Project year-end net income (±5% accuracy required for tax planning)
- Calculate Q4 estimated tax requirement (Form 1040-ES)
- Review S-corporation election timing (Form 2553)
- Schedule equipment purchases for cost segregation analysis
November Strategy & Implementation
Transform October plans into actionable execution
November is execution month. The strategic decisions from October now become concrete actions. This is when you finalize expense acceleration, complete S-corporation elections, and implement retirement plan contributions before the December 31st deadline.
Expense Acceleration Opportunities
Under IRC Section 162, ordinary and necessary business expenses reduce taxable income dollar-for-dollar. If you accelerate $100,000 in business expenses to November, you reduce 2026 taxable income by $100,000, saving approximately $35,000 in federal, state, and self-employment taxes (illustrative combined 35% effective rate).
Deductible Immediately
- ✓ Professional services & consulting
- ✓ Insurance premiums (liability, health)
- ✓ Office supplies & subscriptions
- ✓ Equipment repairs & maintenance
- ✓ Travel & client entertainment
- ✓ Advertising & marketing
Section 179 Expensing
- ✓ New or used tangible property
- ✓ 100% first-year deduction
- ✓ 2026 limit: $2,560,000
- ✓ Must be placed in service by Dec 31
- ✓ Phaseout begins above $4,090,000 of purchases
- ✓ Limited to business income
Holding ISOs alongside RSUs? Run the AMT calculator for ISO exercises before you exercise.
Use the mega backdoor Roth calculator to size the after-tax contribution your plan allows.
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December Critical Moves
Final 31 days to lock in your 2026 tax position
December is the deadline month. Every action taken by December 31st at 11:59 PM is tax-deductible in 2026. The IRS enforces a strict bright-line rule: transactions after midnight on December 31st belong to 2027. This creates both urgency and opportunity for last-minute tax optimization.
December 31st Deadline Items
Solo 401(k) Contributions
Employee deferral election deadline: December 31st. S corp owners run it through final payroll. A sole proprietor with no employees can adopt a first plan after year-end, by the filing deadline without extensions (IRS Pub. 560). 2026 limit: $72,000 combined (age 50+: $80,000 with the $8,000 catch-up).
SEP-IRA Funding
Plan setup and funding deadline: your tax filing deadline, April 15, 2027, or October 15, 2027 with an extension. Limited to 25% of net self-employment income (up to $72,000 for 2026).
Equipment Purchases
Section 179 election: Placed in service by December 31st. Bonus depreciation: 100% first-year deduction. Cost segregation: Property must be owned by year-end.
Charitable Contributions
Cash donations: Deductible by December 31st (proof of payment required). Corporate charitable contributions reduce C-corporation taxable income dollar-for-dollar.
Entity Structure Optimization
S-Corp vs. Sole Proprietorship real-world analysis
Entity structure is the single most impactful tax decision for profitable businesses. The self-employment tax savings alone (15.3% on business income reduction) often exceeds the cost of accounting complexity. As a rule of thumb, an S-corporation election can save 15.3% on the share of income paid as distributions, often 40 to 50 percent of profit after reasonable wages.
Entity Comparison Analysis
| Entity Type | Self-Employment Tax | Owner Liability | Complexity | S-Corp Payroll Required |
|---|---|---|---|---|
| Sole Proprietorship | Full 15.3% on net income | Unlimited | Low | No |
| Partnership | Full 15.3% on guaranteed payments | Unlimited (except LP) | Medium | No |
| S-Corporation | FICA on W-2 wages only; none on distributions | Limited | High | Yes (reasonable compensation) |
| C-Corporation | $0 (paid at entity level) | Limited | High | Required for payroll |
The S-corporation election is optimal for service businesses earning $80,000+ annually. Below $80,000, accounting complexity often outweighs tax savings. The IRS expects reasonable W-2 wages in S-corporations, typically 50-60% of net business income, to prevent aggressive income splitting.
Read our full tax planning guide →Estimated Tax & Penalty Avoidance
How to calculate Q4 payments and avoid the 7% underpayment penalty
Estimated tax penalties accumulate through penalty interest. The current rate is 7% per annum as of Q3 2026, and it resets each quarter based on the federal short-term rate. This is a real tax cost, not deductible against income, that's entirely avoidable with proper calculation.
2026 Estimated Tax Worksheet
Line 1: Projected 2026 Net Income$_________
Line 2: Less: Deductions (itemized or standard)$_________
Line 3: Taxable Income (Line 1 - Line 2)$_________
Line 4: Federal Income Tax on Line 3 (2026 rates)$_________
Line 5: Self-Employment Tax (92.35% × Line 1 × 15.3%)$_________
Line 6: Total 2026 Tax Liability (Line 4 + Line 5)$_________
Line 7: Less: W-2 Withholdings$_________
Line 8: Remaining Tax Due (Line 6 - Line 7)$_________
Line 9: Q4 Estimated Payment (Line 8 × 25%)$_________
Bonus Depreciation & Cost Segregation
100% first-year deduction for qualified property
Bonus depreciation (IRC Section 168(k)) allows a 100% first-year deduction for qualified property placed in service in 2026, and the OBBBA made the 100% rate permanent. This is the most aggressive depreciation method available under the tax code and converts capital purchases into immediate operating expenses.
Bonus Depreciation vs. Section 179
Bonus Depreciation
- ✓ 100% deduction, any amount
- ✓ New or used property
- ✓ Qualified improvement property
- ✓ No business income limitation
- ✓ No AMT adjustment
- ✓ 100% rate permanent under OBBBA
Section 179 Expensing
- ✓ $2,560,000 annual limit (2026)
- ✓ Tangible personal property
- ✓ Some building improvements (roofs, HVAC)
- ✓ Limited to business income
- ✓ No AMT impact
- ✓ Can carryforward unused amounts
Cost segregation is a specialized technique that breaks down buildings into components with shorter depreciation periods. A $2M building purchase might be reclassified as 40% components (5, 7, and 15-year property) vs. 60% building (39-year property). This accelerates deductions by $50,000-$150,000 depending on property composition.
Explore bonus depreciation strategies for your business →Retirement Plan Deadlines & Contributions
2026 limit optimization: $72,000-$80,000 deductions
Retirement plan contributions are the most tax-efficient savings mechanism available. You receive an immediate tax deduction (reduces taxable income) while building tax-deferred wealth. For most Solo 401(k) owners, the employee deferral election deadline is December 31st, 2026.
2026 Retirement Plan Limits
Plan Selection Guide
Solo 401(k)
Ideal for self-employed professionals. Setup: in time to elect deferrals by Dec 31 (sole proprietors with no employees: first plan by the filing deadline, no extension). Employer contribution: return due date, with extensions. Higher contribution limits, investment flexibility, and loan provisions. Administrative burden: Low-medium.
SEP-IRA
Ideal for variable income. Setup and contribution: your filing deadline (with extension). Simple setup, no annual filings, but limited to 25% of net income. Administrative burden: Minimal.
Defined Benefit Plan
Ideal for high-income professionals. Setup: by your filing deadline (SECURE Act). Large contributions (actuarially determined). Complex setup and annual valuations. Administrative burden: High. CPA/pension specialist required.
Documentation & Next Steps
IRS compliance and record-keeping requirements
Tax planning without documentation is a liability, not a benefit. The IRS requires contemporaneous written evidence for deductions. This is especially critical for aggressive strategies like bonus depreciation, S-corporation elections, and entertainment expenses.
Essential Tax Records to Maintain
Income Documentation
- • Invoices sent to clients (copy)
- • Bank deposits (receipts)
- • Client contracts (signed)
- • 1099s received (copies)
- • Sales records or point-of-sale logs
Expense Documentation
- • Receipts & invoices (itemized)
- • Credit card statements
- • Bank check images
- • Mileage log (if vehicle deduction)
- • Home office calculation worksheet
Asset & Depreciation
- • Equipment purchase invoices
- • Date placed in service (proof)
- • Serial numbers & descriptions
- • Cost segregation reports
- • Depreciation schedule (print)
Entity & Planning Elections
- • Form 2553 (S-corp election)
- • Retirement plan documents
- • Section 179 election statement
- • Entity formation documents (LLC/C-Corp)
- • Tax return copies (all years)
Your Year-End Action Checklist
The decisions you make in October, November, and December directly impact your 2026 tax liability. A business owner who implements the strategies in this checklist could reduce taxable income by $200,000-$500,000, potentially saving $70,000-$175,000 in taxes depending on income and rates.
View complete business expense categories →Frequently Asked Questions
When should I start year-end tax planning?
Ideally, begin in September to have 4 months for strategy implementation. October is the absolute minimum to capture major tax-saving opportunities. Any later and you lose critical windows for certain deductions and entity elections.
How much can I save with a 1099 independent contractor strategy?
Worker classification follows the IRS common law tests, not preference. When a role legitimately qualifies as an independent contractor relationship, the business avoids the employer share of payroll taxes (7.65%, roughly $11,475 on $150,000 of pay) plus unemployment taxes and benefit costs. Misclassifying an employee as a contractor triggers back taxes and penalties, so document the relationship carefully.
What is bonus depreciation and how much can it save?
Bonus depreciation allows a 100% first-year deduction on qualified property purchases, and the OBBBA made the 100% rate permanent for property acquired after January 19, 2025. A $500,000 equipment purchase could generate $175,000 in tax savings (35% illustrative combined rate), reducing taxable income immediately.
Are there penalties for underpaying estimated taxes?
Yes. Underpayment interest accrues from each missed quarterly due date. The rate is 7% annually as of Q3 2026 and resets each quarter. A $50,000 shortfall carried for a full year would cost roughly $3,500 in penalty interest, so proper Q4 calculations matter.
Can I deduct business losses on my personal tax return?
This depends on entity structure (S-corp, partnership, sole proprietorship) and passive activity rules. Passive losses generally only offset passive income, though rental real estate has a special $25,000 allowance for active participants that phases out at higher incomes. Active business losses in sole proprietorships offset other income dollar-for-dollar, subject to excess business loss limits.
What business expenses can I accelerate before December 31st?
Under IRC Section 162, ordinary and necessary business expenses are fully deductible: office supplies, professional services, insurance premiums, equipment repairs, and subscriptions. Capital purchases above the $2,500 de minimis safe harbor generally require depreciation, while Section 179 expensing allows up to $2,560,000 in 2026.
Ready to Optimize Your 2026 Tax Position?
Our tax strategists can implement these strategies for your specific situation. Book a free 30-minute initial consultation to discuss your year-end planning.
Tax planning slots are limited before year-end.
Related Tax Planning Resources
Comprehensive Tax Planning Guide
Full-year tax strategy for businesses of all sizes.
Estimated Tax Penalty Calculator
Compute your Q4 underpayment liability and safe harbor options.
Bonus Depreciation & Cost Segregation
100% first-year deduction strategies for capital equipment.
Complete Deductible Expense List
IRC Section 162 deductions organized by category with examples.
Year End Tax Planning for Small Business Owners
The done-with-you version of this checklist: a CPA runs the projection and the moves before December 31.