New Haven Small Business Tax Tip: Get Ready for the Q3 Estimated Tax Deadline

August 24, 2026 • News

NEW HAVEN, CONNECTICUT : JOSE’S TAX SERVICE : AUGUST 24, 2026

For many self-employed individuals and small business owners, the third 2026 estimated tax payment is due Tuesday, September 15, 2026. The deadline applies to federal estimated tax payments made with Form 1040-ES, Estimated Tax for Individuals. Connecticut estimated income tax payments are generally made with Form CT-1040ES, Estimated Connecticut Income Tax Payment Coupon for Individuals.

This deadline matters because estimated payments cover income that is not subject to regular wage withholding. That may include sole proprietorship income, freelance revenue, gig work, partnership income, S corporation income, rental income, interest, dividends, and other taxable sources.

File and pay on time. A payment that is late or insufficient may lead to penalties, interest, or an underpayment notice. Use the following process to prepare your New Haven business records and complete the Q3 payment accurately.

Why the September 15 Deadline Matters!

The federal estimated tax system generally divides the annual required payment into four installments:

April 15, 2026
June 15, 2026
September 15, 2026
January 15, 2027

For Connecticut calendar-year taxpayers, the same quarterly structure generally applies. By September 15, 75% of the required annual payment should have been paid.

Estimated tax is not a separate business tax return. It is a prepayment of the income tax and self-employment tax expected to be reported on your individual return. For many sole proprietors, the business activity is reported on Schedule C (Form 1040), Profit or Loss From Business. The resulting income flows to the individual federal and Connecticut returns.

You should review your payment requirement if:

Your New Haven business income increased during the year.
You started a new freelance or consulting activity.
You received a large contract, commission, or capital gain.
Your deductions changed significantly.
Your spouse changed jobs or withholding.
You made fewer estimated payments than planned.
You formed an LLC, partnership, or S corporation.
You moved into or out of Connecticut.

The IRS and Connecticut Department of Revenue Services (DRS) may assess underpayment charges when tax is not paid in the required amount by each installment date. Paying more later does not always eliminate an earlier installment shortfall.

Determine Whether You Must Make an Estimated Payment!

Under the general federal rule, you may need to make estimated tax payments when both conditions apply:

You expect to owe at least $1,000 in federal tax for 2026 after withholding and refundable credits.
You expect your withholding and refundable credits to be less than the smaller of:
- 90% of the tax shown on your 2026 return, or
- 100% of the tax shown on your 2025 return if that return covered a full 12 months.

For higher-income taxpayers, the prior-year safe-harbor percentage may be 110% rather than 100%. Review the instructions to Form 1040-ES for the applicable threshold and filing status.

Connecticut uses a similar framework. DRS states that estimated Connecticut income tax payments may be required when:

Your expected Connecticut income tax after withholding and applicable Pass-Through Entity Tax (PE Tax) credits is at least $1,000; and
Your Connecticut withholding and credits are less than your required annual payment.

The Connecticut required annual payment is generally the lesser of 90% of the current-year Connecticut tax or 100% of the prior-year Connecticut tax, when the prior-year return covered a full 12 months.

Do not assume that a federal payment automatically satisfies your Connecticut obligation. Calculate and pay each liability separately.

Calculate the Q3 Amount Using Current Records!

Use a current estimate instead of relying only on last year’s payment schedule. A practical calculation process is:

Project full-year gross revenue.
Start with revenue received through August 31. Add signed contracts, recurring customer revenue, expected fourth-quarter sales, and other reasonably anticipated income.
Project deductible business expenses.
Include ordinary and necessary expenses that are properly connected to the business. Common categories may include advertising, software, professional fees, supplies, business insurance, rent, utilities, merchant fees, and eligible vehicle expenses.
Calculate projected net business income.
Subtract eligible business expenses from business revenue. Do not deduct personal expenses. Do not treat owner draws from a sole proprietorship as deductible business expenses.
Include self-employment tax.
Self-employment tax may apply to net earnings from self-employment. The 2026 Form 1040-ES instructions include a Self-Employment Tax and Deduction Worksheet for this calculation.
Account for other household income.
Add wages, interest, dividends, rental income, retirement income, capital gains, and other taxable items. Include your spouse’s income when filing jointly.
Apply deductions and credits carefully.
Consider the qualified business income deduction, retirement contributions, health insurance deductions, and credits that may apply. Confirm eligibility before reducing the estimate.
Calculate the annual required payment.
Compare the current-year projection with the prior-year safe-harbor method. Use the method that applies to your circumstances.
Subtract prior payments and credits.
Review federal and Connecticut payment confirmations. Apply any prior-year overpayment that was elected for credit.
Determine the Q3 amount.
Under a standard equal-installment approach, the Q3 payment is generally one-quarter of the required annual payment. If prior payments were missed or changed, the amount needed by September 15 may differ.

Example: Federal Estimated Tax Calculation

Assume your projected federal required annual payment is $24,000. You paid $6,000 in April and $6,000 in June.

Under a standard four-installment schedule:

Required annual payment: $24,000
Standard quarterly installment: $6,000
Payments made through Q2: $12,000
Q3 payment due September 15: $6,000
Remaining standard Q4 payment: $6,000

This is an illustration only. Your calculation may change because of withholding, credits, income fluctuations, prior-year overpayments, or the annualized income installment method.

Use the Annualized Method When Income Is Uneven!

A standard four-payment schedule may not accurately reflect a seasonal New Haven business. Restaurants, contractors, retailers, event professionals, and tourism-related businesses may receive income unevenly throughout the year.

If your income was substantially lower during earlier periods and increased during the summer, calculate whether the annualized income installment method is appropriate. This method matches estimated payments more closely to the timing of your income.

For federal purposes, review Publication 505, Tax Withholding and Estimated Tax, and the instructions to Form 2210, Underpayment of Estimated Tax by Individuals, Estates, and Trusts.

For Connecticut purposes, review the DRS guidance for Informational Publication 2018(11), A Guide to Calculating Your Annualized Estimated Income Tax Installments, and Worksheet CT-1040 AES.

Do not use the annualized method casually. The calculations are technical. Maintain period-by-period income and expense records. Attach the required schedules when your tax return is filed.

Pay Federal and Connecticut Estimates Through Official Channels!

Pay the federal Q3 estimate using one of the payment methods listed by the IRS:

IRS Online Account
IRS Direct Pay
Electronic Federal Tax Payment System (EFTPS)
Debit card, credit card, or digital wallet
Electronic funds withdrawal through approved tax software or a tax professional
Check or money order using the Q3 Form 1040-ES payment voucher

If you use EFTPS, the IRS states that payments must be scheduled by 8 p.m. Eastern Time at least one calendar day before the tax due date. Save the confirmation number and payment record.

For Connecticut, use myconneCT to make an electronic payment. You may also use Form CT-1040ES when paying by mail. DRS provides payment confirmation for electronic transactions. Save the confirmation with your tax records.

Do not combine federal and Connecticut payments. Use the correct taxpayer identification number, tax year, payment type, and jurisdiction.

Let Bookkeeping Make the Deadline Routine!

Accurate bookkeeping converts estimated tax preparation from a last-minute exercise into a controlled monthly process. Before calculating your Q3 payment, complete the following bookkeeping review:

Reconcile business bank accounts.
Match the accounting records to bank statements through August 31.
Reconcile business credit cards.
Confirm that charges are assigned to the correct expense categories.
Separate business and personal transactions.
Reclassify personal purchases and owner distributions. Do not claim them as business deductions.
Record all revenue sources.
Include checks, credit card receipts, ACH deposits, digital payments, marketplace payments, and unpaid invoices when using the appropriate accounting method.
Review merchant processor reports.
Compare gross customer receipts with net deposits. Processing fees may be deductible business expenses, but they should be recorded separately.
Review accounts receivable and accounts payable.
Identify customer balances, unpaid bills, recurring obligations, and unusual transactions.
Verify vehicle and home-office records.
Maintain mileage logs, business-purpose notes, dates, locations, and supporting receipts. Home-office deductions require exclusive and regular business use under applicable rules.
Upload and label receipts.
Keep invoices, contracts, receipts, bank statements, and payment confirmations in an organized digital file.
Prepare a year-to-date profit-and-loss statement.
Compare revenue, expenses, and net income with the same period last year.
Create a tax reserve.
Set aside funds for federal income tax, self-employment tax, Connecticut income tax, and any business-level obligations.

A clean bookkeeping file also improves deduction review. It helps identify expenses that may have been overlooked, reduces duplicate entries, and provides documentation if a tax position is questioned.

Review Entity-Specific Requirements Before Paying!

The correct estimated tax procedure depends on your business structure.

Sole proprietors generally report business income on Schedule C and may make estimated payments through Form 1040-ES.
Single-member LLC owners are often treated as sole proprietors for federal income tax unless an election applies.
Partners may receive Schedule K-1 income and should coordinate individual estimates with partnership reporting.
S corporation shareholders should coordinate shareholder estimates with payroll, withholding, Form 1120-S reporting, and any applicable Connecticut requirements.
C corporations generally follow a separate corporate estimated tax process.

Connecticut Pass-Through Entity Tax rules may also affect the calculation. Do not use a standard individual estimate without reviewing the entity’s tax classification and prior filings.

Complete Your September 15 Checklist Now!

Before the deadline, complete these steps:

Close your books through August 31.
Review year-to-date revenue and expenses.
Project full-year net income.
Calculate federal and Connecticut estimates separately.
Compare the projection with the applicable safe-harbor amount.
Apply prior payments and overpayment credits.
Check whether the annualized method is appropriate.
Schedule federal and Connecticut payments through official portals.
Save confirmation numbers and payment records.
Contact a tax professional if your entity, income, or deductions changed materially.

Jose’s Tax Service provides personalized tax planning, tax preparation, bookkeeping, and business support for New Haven business owners and self-employed individuals. Appointments are available in person and virtually. Visit the virtual tax services page or schedule a tax appointment.

The September 15, 2026 Q3 estimated tax deadline should be treated as a planning checkpoint. Do not wait until the payment date to discover that your records are incomplete. Organize the books, calculate the estimate, pay through the proper channel, and retain the documentation.

Official IRS Q3 tax calendar | 2026 Form 1040-ES | Connecticut DRS tax information

Category: Tax Planning | Tags: small business tax, New Haven business, deductions, tax strategy.