The Entrepreneur's Tax Planning Checklist
A Proactive Tax Planning Calendar, Quarter by Quarter
What Should Be on an Entrepreneur's Tax Planning Checklist?
Quick Answer: An entrepreneur's tax planning checklist is a dated list of the decisions that stop being available once a deadline passes. For the 2026 tax year that means four estimated-tax installments (April 15, June 15 and September 15, 2026, then January 15, 2027), a March 16 deadline covering both pass-through returns and the S-corporation election, retirement plans that must be established by the return deadline, and the items that have to be executed by December 31.
This page sits under our tax planning for business owners pillar and covers one part of it: the calendar. Which strategies belong in your plan is a separate question. This page is about when each one has to be decided, and which are already closed by the time most owners start thinking about taxes.
It does not attach a dollar figure to planning early rather than late. No published research we could locate measures that difference, and a number we cannot source is not one we will publish. What can be stated precisely is the deadline attached to each decision, and every date below is cited to the IRS document that sets it.
When Are Quarterly Taxes Due in 2026?
Four estimated-tax installments, and none of them shift this cycle. For the 2026 tax year, calendar-year individuals owe estimated tax on April 15, June 15 and September 15, 2026, then January 15, 2027, per Form 1040-ES. All four fall on weekdays, so the weekend-and-holiday rule in IRC Section 7503 moves none of them. Several other dates on the 2026 calendar did shift, and those are the ones most often missed.
| Date | What is due | Authority |
|---|---|---|
| February 2, 2026 | Forms W-2 and 1099-NEC for 2025 — both filed and furnished to recipients. The statutory January 31 fell on a Saturday. | IRS first-quarter tax calendar |
| March 16, 2026 | Calendar-year Forms 1065 and 1120-S for 2025, with Schedules K-1 to partners and shareholders. The statutory March 15 fell on a Sunday. | IRS first-quarter tax calendar |
| March 16, 2026 | Form 2553 to elect S-corporation treatment effective for the 2026 tax year — two months and 15 days after the year begins. | Form 2553 instructions; IRS first-quarter tax calendar |
| April 15, 2026 | First 2026 estimated-tax installment. Also: 2025 Form 1040 and calendar-year Form 1120, and the last day to fund an IRA or HSA for 2025. | Form 1040-ES; IRS Publication 590-A |
| June 15, 2026 | Second 2026 estimated-tax installment. | Form 1040-ES |
| September 15, 2026 | Third 2026 estimated-tax installment. Also: extended 2025 Forms 1065 and 1120-S, and the minimum required contribution for a calendar-year defined benefit plan (8½ months after the plan year ends). | Form 1040-ES; IRC § 430(j) |
| October 1, 2026 | Latest start for a new safe harbor 401(k) covering part of 2026, because the first plan year must run at least three months. This date is arithmetic, not a date the IRS states. | Treas. Reg. § 1.401(k)-3(e)(2) |
| October 15, 2026 | Extended 2025 Form 1040 and extended calendar-year Form 1120. Also the last day to establish and fund a SEP-IRA for 2025 on an extended return. | IRS Publication 560 |
| December 1, 2026 | Approximate last date to add a 3% safe harbor nonelective contribution for 2026: the amendment must be adopted more than 30 days before the plan year closes. A 4% nonelective can be adopted later still. Matching safe harbors cannot use this route. | Notice 2020-86 |
| December 31, 2026 | Charitable gifts, Roth conversions, loss harvesting, annual-exclusion gifts, and any equipment placed in service must be complete. | — |
| January 15, 2027 | Fourth 2026 estimated-tax installment. | Form 1040-ES |
| February 1, 2027 | File the 2026 return and pay the balance in full by this date and the January 15 installment is not required. The statutory January 31 falls on a Sunday this cycle. | IRC § 6654(h); Form 1040-ES |
| April 15, 2027 | 2026 Form 1040, and the last day to fund an IRA or HSA for 2026. An extension does not move either of those two. | IRS Publication 590-A |
One widely repeated rule is wrong: a calendar-year C corporation receives the full six-month extension to October 15, not a five-month extension to September 15. The seven-month extension applies only to C corporations with a June 30 year end beginning before January 1, 2026.
]How Do the Estimated-Tax Safe Harbors Work?
An estimated-tax safe harbor is a payment level that switches off the underpayment penalty whatever you eventually owe. IRC § 6654(d)(1) provides two: 90% of the tax shown on the current year's return, or 100% of the tax shown on the prior year's return. If prior-year adjusted gross income exceeded $150,000 ($75,000 if married filing separately), the second figure becomes 110%. The prior-year return must cover all twelve months.
For an owner whose income is rising, the prior-year harbor is usually the cheaper one: it fixes the required payment against a number already known in January, and the additional tax is simply paid with the return. For an owner whose income is falling, the current-year test costs less cash during the year, but it has to be estimated accurately to hold.
Lumpy income has its own method. The annualized income installment method in IRC Section 6654(d)(2), computed on Form 2210 Schedule AI, replaces the flat quarterly requirement with one based on income actually earned through each period. It is the right tool for a seasonal business, a large gain that lands late in the year, or distributions weighted to the fourth quarter.
The penalty is interest, and the rate moves. IRC Section 6621(a)(2) sets it at the federal short-term rate plus three percentage points, reset every quarter. In 2026 it has run 7% in the first quarter, 6% in the second and 7% in the third; the fourth-quarter rate was not yet announced as of August 1, 2026 (IRS quarterly interest rates). Because the rate resets, there is no single "2026 penalty rate" — the addition is computed period by period over the time each installment is short.
What Belongs in Each Quarter?
The point of a quarterly cycle is not that four meetings are better than one. It is that each quarter has a different job, and doing Q3's job in December does not work.
| Quarter | Fixed deadlines | What the quarter is for |
|---|---|---|
| Q1 — January to March | W-2 and 1099-NEC (February 2, 2026). Forms 1065 and 1120-S (March 16). Form 2553 for a current-year S election (March 16). | Close the prior year's books and reconcile them against what was projected. Choose the estimated-tax method for the year — prior-year harbor or annualized — because that choice governs every payment that follows. If an S election is wanted for this year, this is the only window. |
| Q2 — April to June | First installment and the 2025 Form 1040 or extension (April 15). Second installment (June 15). IRA and HSA funding for 2025 closes April 15. | Read four to five months of actuals against plan and decide whether the estimated-tax method chosen in Q1 still fits. Fund prior-year SEP and solo 401(k) contributions if the return was extended. Entity and compensation changes made now have most of the year to run. |
| Q3 — July to September | Third installment, extended pass-through returns, and the defined benefit minimum required contribution (all September 15). A new safe harbor 401(k) must start by October 1. | Nine months of actuals make a full-year projection reliable for the first time. This is the last quarter in which a decision needing lead time — a new plan, an entity change, a property acquisition — can still be implemented rather than merely intended. |
| Q4 — October to December | Extended Form 1040 and Form 1120 (October 15). Safe harbor nonelective amendment (about December 1). Everything else, December 31. | Execute. Roth conversions, loss harvesting, charitable gifts and annual-exclusion gifts are genuinely Q4 decisions because they depend on knowing the year's income. Anything else arriving here for the first time is being decided under a deadline rather than on its merits. |
Which Decisions Need Lead Time?
Most of what a tax plan can do is decided months before the deduction appears. These are the items where the deadline and the decision date are not the same day.
| Decision | The date that governs | Why it needs lead time |
|---|---|---|
| Establishing a retirement plan (SEP, solo 401(k), profit sharing) | The employer's return due date, including extensions — IRC § 401(b)(2), IRS Publication 560 | The plan can be adopted after the year ends, but the contribution still has to be affordable when it is funded, and the design depends on census data that takes time to assemble. |
| First-year elective deferrals by a sole proprietor | The return due date without extensions — IRC Section 401(b)(2) as amended by SECURE 2.0 Act Section 317 | These two dates are routinely conflated. Adoption runs to the extended deadline; the first-year employee deferral does not. |
| Defined benefit or cash balance plan | Established by the extended return due date; minimum required contribution 8½ months after the plan year ends, which is September 15 for a calendar-year plan — IRC § 430(j) | An enrolled actuary sets the contribution, and the funding obligation continues in years when profit does not. This is a multi-year commitment, not a single-year deduction. |
| New safe harbor 401(k) | First plan year of at least three months, so October 1 for a calendar year — Treas. Reg. § 1.401(k)-3(e)(2) | Notice requirements and payroll integration run ahead of the effective date. A 3% nonelective safe harbor can be added far later under Notice 2020-86; a matching safe harbor cannot. |
| S-corporation election | March 16, 2026 for a 2026 effective date — Form 2553 instructions | Reasonable compensation has to be set before payroll runs, not reconstructed afterwards. That decision is its own subject: see S-Corp reasonable salary. |
| Equipment, vehicles and improvements | Placed in service by December 31 — IRC Sections 179 and 168(k) | "Placed in service" is not "ordered" or "paid for." Delivery, installation and availability for use all have to happen inside the year. |
| Charitable gifts and donor-advised fund contributions | December 31 | Transfers of appreciated securities take custodial time, and for 2026 the deduction arithmetic itself changed — see the next section. |
| Annual-exclusion gifts | December 31; the exclusion does not carry forward | $19,000 per recipient for 2026 (Rev. Proc. 2025-32). This belongs to wealth transfer planning rather than income tax, but it shares the same hard deadline and is missed for the same reason. |
| Roth conversions | December 31 | The bracket a conversion fills is only knowable once the year's income is nearly complete, which is exactly why this is a fourth-quarter decision rather than a first-quarter one. |
| IRA and HSA funding | April 15 following the tax year, extensions excluded — IRC Section 219(f)(3), IRS Publication 590-A | The one significant deadline an extension does not move. An owner who extends to October and assumes everything moved with it has already missed this. |
The longest lead times of all belong to an exit. Holding-period and structuring decisions that govern a sale have to be made years ahead of it, and are set out separately under selling a business tax strategies.
]What Changed for 2026, and What Does It Move on the Calendar?
The One Big Beautiful Bill Act (Public Law 119-21, enacted July 4, 2025) changed several rules whose deadlines sit on this calendar. These are the ones that change what a decision is worth rather than only what it is called.
| What changed | The rule for 2026 | What it moves on the calendar |
|---|---|---|
| Bonus depreciation is now two tracks | 100% for qualified property acquired after January 19, 2025 and placed in service in 2026 (IRC § 168(k), as amended by OBBBA Section 70301). Property acquired on or before that date stays on the prior phase-down and takes 20% in 2026 (40% for long production period property and certain aircraft). A written binding contract fixes the acquisition date. | The acquisition date now matters as much as the placed-in-service date. For anything bought under an older contract, the December question is no longer "can it be installed in time" but "which track is this asset on." |
| Section 179 expensing is larger | $2,560,000 for 2026, reduced dollar for dollar once more than $4,090,000 of Section 179 property is placed in service (Rev. Proc. 2025-32; OBBBA Section 70306 set the $2,500,000 and $4,000,000 base amounts that are indexed to these figures). | Still a December 31 placed-in-service test. The larger ceiling is an argument for making the purchase decision against the Q3 projection rather than in the last two weeks of the year. |
| The SALT cap is higher, then disappears | $40,400 for 2026, reduced by 30 cents for every dollar of modified adjusted gross income above $505,000 and never reduced below $10,000. It reverts to $10,000 for tax years beginning after 2029 (IRC § 164(b)(7)). | Where a state pass-through entity tax election is available, that election carries its own state deadline, and most fall well before the federal year end. |
| Charitable deductions now have a floor | For tax years beginning after December 31, 2025, an itemizer deducts only the amount by which gifts exceed 0.5% of contribution base, and a C corporation only the amount above 1% of taxable income (IRC § 170(b)(1)(I) and (2)(A)). The 60%-of-contribution-base ceiling on cash gifts to public charities was made permanent in the same act. | Concentrating two years of giving into one year clears the floor once instead of twice. That is a decision with a December 31 deadline and a custodial lead time in front of it. |
| A new haircut on itemized deductions | Itemized deductions are reduced by 2/37 of the lesser of total itemized deductions or the taxable income above the 37% bracket threshold (IRC § 68, as rewritten by OBBBA Section 70111), first applying to tax years beginning after December 31, 2025. | It lowers what the last dollar of SALT or charitable deduction is worth at the top bracket. That is a reason to model the timing, not a reason to skip the deduction. |
| Domestic research is deductible again | Domestic research or experimental expenditures paid or incurred in tax years beginning after December 31, 2024 are deducted when incurred under IRC § 174A; foreign research is still capitalized and amortized over fifteen years. | The separate election that let smaller taxpayers apply this retroactively to 2022 through 2024 closed on July 6, 2026 and is no longer available. |
| The QBI deduction is permanent | The 20% deduction no longer sunsets, the taxable-income phase-in range widened to $150,000 joint and $75,000 for other filers, and 2026 adds a minimum deduction of $400 for a taxpayer with at least $1,000 of aggregate qualified business income from active trades or businesses (IRC § 199A). Reports of a 23% rate describe a version of the bill that was not enacted. | Where you land in the phase-in range is driven by compensation and distribution decisions taken during the year, which makes this a payroll question rather than a December one. |
| Pass-through entity taxes were left alone | The enacted law made no change to the deductibility of entity-level state taxes paid by a pass-through. Notice 2020-75 remains the operative guidance. | Worth stating because several widely circulated drafts of the bill contained limits that did not survive into law. |
Two tracks exist for bonus depreciation in 2026 and both are stated above because an owner holding property under a pre-January 20, 2025 contract is on the older one. Confirm which track applies to each asset before relying on either figure.
]How Do You Lower Taxable Income as a Business Owner?
Through a small number of ordinary levers, each capped by a number the IRS publishes in advance: deferral into qualified plans, expensing of capital purchases, the timing of income and deductions across two tax years, and charitable transfers. The levers are not exotic. What separates a large result from a small one is usually whether the decision was made while the lever was still available.
Every figure below is the published 2026 amount. They are ceilings a plan is built against, not targets, and none of them is achievable by every business.
| 2026 limit or threshold | Amount | Authority |
|---|---|---|
| Elective deferral, Section 402(g) | $24,500 | Notice 2025-67 |
| Catch-up at age 50 and over, Section 414(v) | $8,000 | Notice 2025-67 |
| Catch-up at ages 60 to 63 | $11,250 (unchanged from 2025) | Notice 2025-67 |
| Total annual additions, Section 415(c) | $72,000 | Notice 2025-67 |
| Defined benefit annual benefit, Section 415(b) | $290,000 | Notice 2025-67 |
| Compensation limit, Section 401(a)(17) | $360,000 | Notice 2025-67 |
| HSA contribution, self-only / family | $4,400 / $8,750 | Rev. Proc. 2025-19 |
| Section 179 expensing limit / phase-out threshold | $2,560,000 / $4,090,000 | Rev. Proc. 2025-32 |
| Annual gift exclusion | $19,000 per recipient | Rev. Proc. 2025-32 |
| Estate and GST basic exclusion | $15,000,000 | Rev. Proc. 2025-32 |
| Top 37% bracket begins | $768,700 joint / $640,600 single | Rev. Proc. 2025-32 |
| Long-term capital gain 15% ceiling | $613,700 joint / $545,500 single | Rev. Proc. 2025-32 |
| Section 199A phase-in begins | $403,500 joint / $201,750 other | Rev. Proc. 2025-32 |
Which of these levers is even available depends on how the business is taxed, which is the subject of our comparison of S corp vs C corp.
Figures are stated for the 2026 tax year and are subject to change. Verify each against the cited IRS document before relying on it.
]What Does Small Business Tax Planning Look Like Across a Full Year?
It looks like a standing cycle rather than a filing event. Four things have to be true for a calendar to work: someone owns it, the projection is refreshed often enough to be worth acting on, decisions are recorded when they are made rather than reconstructed at filing, and the people who execute — the CPA, the bookkeeper, the plan administrator, the custodian — are working from the same set of dates.
Year-end tax planning is the last quarter of that cycle, not a substitute for it. Genuinely fourth-quarter decisions exist: Roth conversions, loss harvesting, charitable timing and bonus timing all depend on knowing what the year actually produced. A new retirement plan, an entity change, a property purchase and an S election are not among them, and an owner whose first tax conversation of the year happens in November is choosing from what is left rather than from what was available.
Tax planning for high net worth individuals differs mainly in how many calendars have to agree. A single-entity owner tracks one set of dates. An owner with an operating company, a holding entity, a qualified plan, a trust and real estate in more than one state has several sets of dates that interact, and a step taken to serve one of them can foreclose something in another. The work is coordination as much as it is tax technique, which is why we treat it as part of tax planning for business owners rather than as a filing task.
A practical test. Take any deduction you expect to claim for this year and ask when the decision behind it had to be made. If that date has already passed, it belongs on next year's calendar, and the useful conversation is about the next twelve months rather than this December.
For the retirement-plan side of that question, our wiki entry on 401(k) plans for business owners sets out the contribution mechanics and current limits in more detail.
Tax Calendar Questions Entrepreneurs Ask
What is the safe harbor for estimated tax payments?
A safe harbor is a payment level that switches off the underpayment penalty regardless of what you ultimately owe. IRC Section 6654(d)(1) provides two: pay 90% of the current year's tax, or pay 100% of the tax shown on last year's return. If your prior-year adjusted gross income was over $150,000 ($75,000 if married filing separately), the prior-year figure rises to 110%. The prior-year return has to cover twelve months for that harbor to be available.
How is the estimated tax penalty calculated?
It is interest rather than a flat fine. IRC Section 6621(a)(2) sets the rate at the federal short-term rate plus three percentage points, and it resets every quarter, so the charge is computed period by period over the days each installment was short. During 2026 the rate has been 7% for the first quarter, 6% for the second and 7% for the third, with the fourth quarter not yet announced as of August 1, 2026. Paying late is expensive but rarely catastrophic; paying the wrong amount all year is usually worse.
What is the annualized income installment method?
It is an alternative way to compute each required estimated-tax installment, set out in IRC Section 6654(d)(2) and calculated on Schedule AI of Form 2210. Instead of assuming income arrives evenly and requiring roughly a quarter of the annual amount each period, it bases each installment on income actually earned through that period. It is worth the extra work when income is seasonal, when a large gain lands late in the year, or when distributions are concentrated in the fourth quarter.
How is tax planning for high net worth individuals different?
The techniques are largely the same; the number of moving calendars is not. An owner with an operating company, a holding entity, a qualified plan, a trust and property in several states has multiple sets of deadlines that interact, and a step taken to serve one can close an option in another. That is why the work is usually organized around coordination and sequence rather than around a list of strategies, and why it runs year-round instead of at filing.
When should year-end tax planning start?
Earlier than year end. The decisions that can only be made in the fourth quarter are Roth conversions, loss harvesting, charitable timing and bonus timing, because each depends on knowing what the year produced. Everything else carrying a December 31 deadline — a new retirement plan, an entity change, a property acquisition — needs lead time, so in practice the fourth quarter executes decisions taken in the second and third.
How do the wealthiest families
keep a tax calendar from slipping?
They give one professional the calendar and the standing to run it. Schedule an assessment and we will map your entities, retirement plans and estimated-tax method against the dates on this page, identify which of this year's decisions are still open and which have already closed, and set the review cadence that keeps the open ones from closing unnoticed — coordinated by a Fractional Family Office®.
Take control of your financial future. Use our free Wealth Waste Calculator® to estimate what your current structure may be costing you each year.
Page last updated: August 1, 2026
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Dew Wealth Management, LLC ("Dew Wealth") is an SEC-registered investment adviser located in Scottsdale, Arizona. Registration does not imply a certain level of skill or training. The information provided in this material is for general informational and educational purposes only and should not be construed as personalized investment, tax, or legal advice. All investing involves risk, including the potential loss of principal.
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