Quarterly estimated taxes are one of the most important—and often overlooked—financial obligations for small business owners. Unlike W-2 employees, business owners don’t have taxes automatically withheld throughout the year. Instead, the IRS expects you to pay taxes quarterly based on your income and expected tax liability. Missing or underpaying these deadlines can lead to penalties, interest charges, and unwanted surprises at year-end.
Q3 estimated taxes are especially important because they represent the final major checkpoint before year-end planning begins. This is where you can catch up, correct course, and stabilize your tax outlook before the last stretch of the year.
This guide walks you through everything you need to prepare for your Q3 estimated taxes with confidence.
Understand What Q3 Estimated Taxes Include
Quarterly estimated taxes typically cover:
– Federal income tax
– Self-employment tax
– State income tax (if applicable)
– Local taxes in certain jurisdictions
If you’re an S-corp owner, estimated taxes might apply to:
– Payroll tax responsibilities
– Owner salary withholding
– Pass-through income
Q3 is due in mid-September, making it an essential checkpoint for accurate tax planning.
Review Your Year-to-Date Profit
Before calculating your Q3 payment, you need accurate bookkeeping through at least the end of Q2.
Review:
– Profit & Loss Statement (P&L)
– Total revenue
– Total expenses
– Net income so far
Your estimated tax payment is based on taxable income—not total revenue—so accurate bookkeeping is essential.
If your books aren’t up to date, estimate conservatively to avoid underpayment penalties.
Look for Major Changes in Income Since Q2
Many businesses experience seasonal swings or mid-year growth. Ask:
– Did revenue increase significantly in Q3?
– Did expenses rise or fall?
– Did you add new revenue streams?
– Did you hire or shift labor costs?
If income increased, your Q3 payment should increase to reflect your higher tax liability.
Review Last Year’s Tax Liability (Safe Harbor Rules)
The IRS offers a safe harbor rule to avoid penalties:
– Pay 100% of last year’s tax liability (110% if AGI > $150,000), OR
– Pay 90% of the current year’s projected liability
If your income varies dramatically month to month, safe harbor may be your best friend.
This lets you avoid penalties even if your current-year income ends up much higher.
Consider Any Tax-Deductible Business Changes This Year
Business deductions reduce your estimated tax liability. Review whether you’ve taken:
– Depreciation
– Section 179 deductions
– Bonus depreciation
– Equipment purchases
– Retirement contributions
– Home office deduction
– Mileage and travel
– Software and subscription costs
– Marketing and advertising expenses
Update your year-to-date deduction totals before calculating Q3 taxes.
Account for Self-Employment Tax
If you’re a sole proprietor, contractor, or partner in an LLC, you must include self-employment tax in your quarterly estimate.
Self-employment tax = Social Security + Medicare
This is an additional 15.3% on net business income.
Many owners forget to calculate this properly, leading to underpayment.
Update Your Estimated Tax Worksheet
Use IRS Form 1040-ES to calculate:
– Adjusted gross income
– Deductions
– Self-employment tax
– Income tax liability
Your Q3 estimated payment should reflect:
– Year-to-date reality
– Expected Q4 performance
– Any tax planning you intend to do before year-end
Factor in S-Corp Owner Salary and Withholding (If Applicable)
S-corp owners pay themselves through payroll, which means withholding taxes automatically.
Ask:
– Has your salary withholding been enough?
– Should your salary be adjusted?
– Are you on track for reasonable compensation rules?
If withholding is accurate, your Q3 estimated payment may be smaller.
Review State and Local Tax Requirements
Not all states require quarterly taxes, but many do.
Check:
– State income tax rules
– Local tax requirements
– Franchise taxes
– Gross receipts taxes
Some states require different due dates or different estimated tax percentages.
Consider Mid-Year Tax Planning Opportunities
Q3 is the perfect time to implement tax-saving strategies because there’s still enough year left to make an impact.
Potential opportunities:
– Retirement contributions (SEP IRA, Solo 401k)
– Accelerated expenses
– Delaying certain income
– Adjusting payroll
– Investing in deductible assets
– Reviewing health insurance tax strategies
Proactive planning now makes Q4 much easier.
Set Aside Funds in a Separate Tax Account
To avoid scrambling, transfer tax money into a dedicated tax savings account.
General guideline:
Set aside 25–35% of net income for taxes.
This varies based on your entity type, state, and tax strategy.
Make Your Q3 Payment Before the Deadline
The Q3 estimated tax payment is generally due:
September 15th
Payments can be made through:
– IRS Direct Pay
– EFTPS
– Your state’s tax portal
– Business bank bill-pay
Late payments incur penalties—even if you intend to catch up later.
Final Thoughts
Quarterly estimated taxes don’t have to feel overwhelming. When your bookkeeping is accurate and your forecasting is realistic, preparing for Q3 becomes a smooth and predictable part of your financial routine. The key is staying proactive—reviewing your numbers regularly and adjusting your estimates as your business evolves.
If you want help calculating your estimated taxes, reviewing your profit, or creating a tax planning strategy for the rest of 2026, Nimble Numbers is here to assist with expert bookkeeping and tax support.
Nimble Numbers provides bookkeeping, payroll, tax planning, and fractional CFO services for small businesses across the United States. Book a free consultation at nimblenumbers.com or call 1-866-448-2424. Less stress, more success.
