Here's how most business owners experience taxes: panic in February, scramble in March, write a big check in April, and forget about it until next February. Rinse and repeat, year after year, while quietly overpaying tens of thousands of dollars that a little calendar discipline could have saved.
The business owners who consistently pay the least in taxes aren't smarter—they're more systematic. They treat tax planning like a quarterly business review, not an annual fire drill. This guide gives you a month-by-month tax planning calendar so you know exactly what to do, when to do it, and how much it can save you.
Key Takeaways
- Quarterly estimated taxes are due April 15, June 15, September 15, and January 15 — missing them costs you penalty interest
- The biggest savings windows are Q3 and Q4 — by July you have enough data to project your year and time your moves
- December 31 is an absolute deadline — retirement contributions, equipment purchases, and entity elections must happen before year-end
- January is for entity structure review — if you should be an S-Corp, the election deadline is typically March 15
- Year-round bookkeeping is required — you can't plan what you can't see; clean books are the foundation of effective tax planning
Table of Contents
Q1 (January–March): Review, Reset, and Elect
January through March is a transitional period—you're closing out last year while setting up for this one. Most business owners are reactive in Q1, just trying to gather documents. But smart planners use Q1 to make moves that will matter all year.
January
- Gather all income documents (1099s, bank statements, investment accounts)
- Close out last year's bookkeeping—get everything reconciled before February
- Review prior year tax return for missed deductions or strategies
- Set up or update your chart of accounts for the new year (see our chart of accounts guide)
- Make a prior-year SEP IRA contribution if you have not yet done so (deadline: tax return due date with extensions)
February
- Work with your CPA or tax strategist on the prior year return
- Identify any strategies that should have been implemented—use them as a checklist for this year
- Review your entity structure: should you be an S-Corp? (Election due March 15 for current-year treatment)
- Discuss retirement plan contributions for the prior year (if applicable)
March
- March 15: S-Corp election deadline (Form 2553) for current-year treatment if operating as an S-Corp
- March 15: Partnership and S-Corp returns due (or request extension)
- Establish Q1 estimated tax payment amount based on projected income
- Set up payroll if you elected S-Corp status—you must run a reasonable salary starting now
The S-Corp election deadline is one of the most commonly missed tax planning opportunities. If you're a single-member LLC with net income over $50,000–$60,000, you almost certainly should be an S-Corp—and the election must be filed by March 15 to take effect for the current tax year. Miss that date and you're stuck paying full self-employment tax for another full year. Every year I see business owners who learn about this in October and have to wait until next January to implement it. Don't be that person.
Q2 (April–June): Mid-Year Check-In and Estimated Taxes
Q2 is when the year really starts—your first full quarter is behind you, you have real data to work with, and your Q1 estimated tax payment is due on April 15. This is the time to set your baseline projection for the year.
April
- April 15: Q1 estimated tax payment due (federal; check your state deadline)
- April 15: Individual returns due (or file extension)
- Review Q1 income vs. prior year—are you on pace for a higher or lower income year?
- Adjust S-Corp salary if your income trajectory has shifted significantly
- Make Q1 Solo 401(k) or SEP contribution if you're self-employed
May–June
- June 15: Q2 estimated tax payment due
- Project full-year income with your bookkeeper or fractional CFO
- Review retirement contribution pace—are you on track to maximize for the year?
- Begin thinking about major equipment purchases: will you need them before year-end?
- Review deductible business expenses—are there legitimate costs you've been paying personally?
Q3 (July–September): Equipment and Income Projection
Q3 is where proactive tax planning really earns its keep. By July, you have six months of data and enough runway to make meaningful decisions before December 31. This is when the best tax planners get busy.
July–August
- Run a year-end tax projection with your advisor or fractional CFO
- Identify whether you're on track for a higher-than-expected income year (triggers year-end planning urgency)
- Evaluate equipment needs for the next 12 months: is it worth buying before December 31 for Section 179 or bonus depreciation?
- Review retirement plan options—should you set up a defined benefit or cash balance plan for this year?
- Evaluate whether to accelerate any deductible business expenses into this year
September
- September 15: Q3 estimated tax payment due
- September 15: Extended partnership and S-Corp returns due
- Finalize year-end tax projection and identify specific action items
- Order/purchase equipment before year-end if the tax math makes sense
- If you haven't set up a retirement plan yet, do it now—some plans must be established before December 31
The Q3 tax projection meeting is the single most valuable hour you can spend on your business finances each year. By September, I can typically tell a client exactly how much they're going to owe, what we can still do to reduce it, and what those moves are worth in dollars. That's the meeting that makes the December 31 scramble unnecessary. If your advisor isn't scheduling this call with you every year, you're leaving money on the table.
Q4 (October–December): Year-End Moves That Save Real Money
Q4 is crunch time. Every decision you make (or don't make) before December 31 directly affects your tax bill. Here's how to maximize the final quarter.
October
- October 15: Extended individual tax returns due—no more extensions after this
- Review Q3 income data and update year-end projection
- Finalize equipment purchase decisions—equipment must be placed in service by December 31 to count for this year
- Review payroll/salary levels for S-Corp owners—adjust if necessary
- Accelerate any outstanding invoices (or delay them, depending on income projection)
November
- Make retirement contributions or maximize them before year-end (Solo 401(k) elective deferrals must be elected before December 31)
- Review business meals, travel, and marketing expenses—are you missing deductible costs?
- Prepay business expenses that will be deductible in the current year (rent, insurance, subscriptions)
- Consider charitable contributions if they align with your tax strategy
- Review your bookkeeping for the year—ensure it's complete and accurate (see our guide to audit-proof bookkeeping habits)
December
- December 31: Hard deadline for ALL year-end tax strategies—equipment placed in service, retirement contributions elected, entity elections
- Close your books for the year as of December 31
- Send year-end bonus checks to employees (if applicable) before December 31 for the deduction
- Pay any outstanding business invoices before December 31 (cash basis taxpayers)
- Collect W-9s from any contractors you paid more than $600 this year
- Schedule January review meeting with your tax advisor
Key Tax Deadlines at a Glance
| Date | What's Due | Who It Affects |
|---|---|---|
| January 15 | Q4 estimated tax payment | Self-employed and small business owners |
| March 15 | S-Corp/Partnership returns; S-Corp election deadline | S-Corps, partnerships |
| April 15 | Q1 estimated tax; Individual returns due | All individual filers |
| June 15 | Q2 estimated tax payment | Self-employed and small business owners |
| September 15 | Q3 estimated tax; Extended S-Corp/Partnership returns | All applicable filers |
| October 15 | Extended individual returns due (final deadline) | Individual filers on extension |
| December 31 | Equipment placed in service; Retirement elections; All year-end strategies | ALL business owners |
The Costly Mistakes of April-Only Thinking
When you only think about taxes in April, here's what you miss:
- Underpayment penalties: If you don't make quarterly estimated payments and you owe more than $1,000, the IRS charges interest on the unpaid amount—typically around 8% annually
- Missed equipment timing: Equipment must be placed in service by December 31. If you buy it January 2 of next year, you wait another full year for the deduction.
- Missed retirement contributions: Solo 401(k) elective deferrals must be elected before December 31. You cannot go back and make them retroactively.
- No S-Corp election: The March 15 deadline passes every year. Every year you miss it without acting costs you $5,000 to $15,000 or more in unnecessary SE tax.
- No ability to defer income: If you invoice clients in December vs. January, that affects your taxable income for the year. Cash basis taxpayers can't plan this after the fact.
The solution to all of these is the same: a year-round planning relationship with someone who knows your numbers and proactively guides you through these decisions. See our guide on proactive tax planning for the full framework, or read about what it means to have a CPA who actually plans your taxes rather than just filing them.
Frequently Asked Questions
When are quarterly estimated tax payments due?
Federal estimated tax payments are due four times per year: April 15 (Q1), June 15 (Q2), September 15 (Q3), and January 15 of the following year (Q4). Missing these deadlines can result in underpayment penalties.
What is the most important tax planning month for business owners?
October and November are arguably the most important months for proactive tax planning. By then you have a clear picture of your annual income and there is still time to implement strategies like retirement contributions, equipment purchases, and income deferral before December 31.
What are the biggest tax mistakes business owners make each year?
The three most common and costly mistakes are: (1) failing to make quarterly estimated tax payments on time, (2) missing the December 31 deadline for retirement contributions and equipment purchases, and (3) not reviewing entity structure annually to ensure the optimal tax treatment.
The Bottom Line
Taxes are not an April problem—they're a year-round strategy. The business owners who pay the least in taxes are the ones who act in July, October, and December, not February. Start treating tax planning as a calendar item, not a crisis response.
About the Author
Tom Woolley, MBA
Tom Woolley is a fractional CFO who has spent 11+ years helping business owners take control of their finances. He works with contractors, dental and medical practices, and professional service firms across the country.
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