Morning: Small Business Tax Tips (New Haven): Q3 Estimated Taxes Due September 15 : A 2026 Checklist for New Haven Business Owners

New Haven, Connecticut : Jose’s Tax Service : September 12, 2026

Category: News | Additional Category: Tax Planning | Tags: New Haven, IRS, Connecticut taxes, estimated taxes, small business tax, tax preparation

The Q3 2026 federal estimated tax payment is due Tuesday, September 15, 2026. The deadline is three days away.

This payment generally covers the estimated tax associated with income received during the third payment period: June 1 through August 31, 2026. New Haven business owners, self-employed professionals, independent contractors, partners, and corporations should review their year-to-date income and submit the correct payment promptly.

A missed or insufficient installment may lead to an underpayment penalty, even if the full tax liability is paid when the annual return is filed.

Confirm Whether You Must Pay!

Estimated tax payments apply to income that is not fully subject to withholding. This may include self-employment income, business profits, interest, dividends, rents, capital gains, and other taxable income.

Individuals and pass-through business owners

You generally should make federal estimated tax payments if both conditions apply:

1. You expect to owe at least $1,000 in federal tax for 2026 after subtracting withholding and refundable credits.
2. Your expected withholding and refundable credits are less than the smaller of:
   • 90% of your expected 2026 tax, or
   • 100% of your 2025 tax, or 110% of your 2025 tax if your 2025 adjusted gross income exceeded $150,000. The threshold is $75,000 for married taxpayers filing separately.

This rule commonly affects:

• Sole proprietors filing Schedule C (Form 1040).
• Independent contractors.
• Freelancers and consultants.
• Partners receiving income reported on Schedule K-1 (Form 1065).
• S corporation shareholders receiving pass-through income.
• Taxpayers with substantial investment or rental income.
• Individuals whose W-2 withholding does not cover their total tax liability.

Review the IRS guidance on estimated tax requirements and the current Form 1040-ES, Estimated Tax for Individuals before calculating the payment.

Corporations

A corporation generally must make federal estimated tax installments if it expects to owe $500 or more in tax for the year. Corporate rules depend on the entity’s tax classification, taxable income, prior-year liability, and filing status.

Do not assume that an LLC, S corporation, or corporation follows the same payment process. The business entity may have a separate federal obligation, while owners may also owe individual estimated tax on pass-through income.

Review the entity’s federal filing requirements and payment history before submitting the installment.

Calculate the September 15 Installment Correctly!

The IRS divides the calendar year into four estimated tax payment periods:

The September installment is not necessarily a simple calculation based only on three months of profit. Estimated tax is generally calculated using annual projected income, deductions, credits, withholding, and prior payments.

Use this process:

1. Update gross receipts through August 31.
2. Record business expenses paid or incurred through the applicable accounting period.
3. Estimate remaining 2026 revenue and expenses.
4. Include self-employment tax where applicable.
5. Account for federal withholding from wages, pensions, or other sources.
6. Subtract estimated payments already made for April and June.
7. Compare the result with the safe harbor amount.
8. Submit the September installment by Tuesday, September 15.

Use the 2026 Form 1040-ES worksheet for an individual estimate. Maintain a copy of the completed worksheet and the payment confirmation with the business tax records.

Use an Approved Payment Method!

Select the payment method that matches the taxpayer or entity.

IRS Direct Pay

Individuals may use IRS Direct Pay to make an electronic payment directly from a bank account. Confirm the tax year, payment type, taxpayer identification information, and bank details before authorizing the transaction.

Save the confirmation number. A bank statement alone may not provide sufficient documentation of the payment selection.

Electronic Federal Tax Payment System

Businesses and individuals may use the Electronic Federal Tax Payment System (EFTPS) for scheduled federal tax payments.

EFTPS enrollment and verification may require advance preparation. Do not wait until the final hours if the account has not been established. Review the settlement date and allow sufficient processing time.

Form 1040-ES

Individuals may use Form 1040-ES, Estimated Tax for Individuals to calculate the amount due and, when applicable, submit a payment voucher.

A paper voucher does not replace the payment itself. Confirm that the payment is correctly directed to the taxpayer’s 2026 estimated tax account.

Credit card, debit card, and other electronic payment options may also be available through the IRS. Processing fees may apply.

Apply the Safe Harbor Rules!

The federal safe harbor rules can reduce exposure to an estimated tax underpayment penalty. Generally, a taxpayer may avoid the penalty by timely paying at least:

• 90% of the current-year tax liability, or
• 100% of the prior-year tax liability, or
• 110% of the prior-year tax liability for taxpayers above the applicable prior-year adjusted gross income threshold.

The required amount must be paid through a combination of withholding and timely estimated installments. Paying the total amount late may not produce the same result as paying the required installments on schedule.

Safe harbor protection does not eliminate the need to review the actual tax liability. A business owner may still owe a substantial balance when filing the 2026 federal return.

If income is uneven, use the annualized income method. Publication 505, Tax Withholding and Estimated Tax explains the calculation. Form 2210, Underpayment of Estimated Tax by Individuals, Estates and Trusts, including Schedule AI when applicable, may be required to document annualized income.

Review Connecticut Requirements!

Connecticut estimated tax obligations should be reviewed separately from federal requirements.

For Connecticut individual income tax, Form CT-1040ES, Estimated Connecticut Income Tax Payment Coupon, generally applies to taxpayers who expect to owe state income tax that is not sufficiently covered by withholding or credits. The Connecticut Department of Revenue Services (DRS) lists September 15, 2026 as the third estimated payment deadline for calendar-year taxpayers.

For 2026, the September installment generally represents 25% of the required annual payment, with approximately 75% of the required annual payment due cumulatively after the third installment.

Business entities should review the applicable Connecticut requirements, including Form CT-1120 ES, Estimated Connecticut Corporation Business Tax Payment Coupon, where applicable. Connecticut rules may differ based on the entity type, tax classification, income, and filing history.

Consult the Connecticut Department of Revenue Services tax information page and the applicable 2026 form instructions. Do not assume that a federal payment automatically satisfies the Connecticut obligation.

Complete This Three-Day Checklist!

Before Tuesday, September 15, complete these steps:

1. Reconcile bookkeeping records through August 31.
2. Separate personal and business transactions.
3. Review gross receipts, payroll, inventory, mileage, and deductible expenses.
4. Update the federal Form 1040-ES calculation.
5. Review the prior-year safe harbor amount.
6. Calculate the Connecticut estimated tax payment separately.
7. Confirm whether the payment is individual, business, or corporate.
8. Submit the federal payment through Direct Pay, EFTPS, or the appropriate method.
9. Submit the Connecticut payment through the applicable DRS process.
10. Save confirmations, worksheets, and payment records.
11. Schedule a year-end projection before the January 15, 2027 installment.

Do not delay because final 2026 income is not yet known. An estimate can be revised as new information becomes available. A missed deadline, however, can increase penalty exposure and complicate year-end planning.

Request Professional Review Before the Deadline!

Estimated tax calculations should reflect the full tax profile, not only the current bank balance. A proper review may identify self-employment tax, pass-through income, withholding adjustments, Connecticut obligations, deductible expenses, and quarterly payment discrepancies.

Jose’s Tax Service provides personalized federal and Connecticut tax preparation, estimated tax planning, bookkeeping support, and virtual or in-person appointments for New Haven business owners and clients throughout Connecticut.

Book a tax appointment or request a quote. Same-day availability may be available.

Jose’s Tax Service
Phone: 475-254-9373
Website: josestaxservice.com

Practical reminder: The Q3 2026 federal and Connecticut estimated tax deadline is Tuesday, September 15, 2026. File or pay promptly. Keep every confirmation. Consult a qualified tax professional regarding your specific circumstances.