Morning: Small Business Tax Tips (New Haven): Q4 Estimated Taxes, How New Haven Business Owners Avoid Underpayment Penalties Before January 15, 2027

September 25, 2026 • News

New Haven, Connecticut, Jose’s Tax Service, September 25, 2026

Small business owners and self-employed individuals must review fourth-quarter estimated tax obligations before January 15, 2027. The payment may apply to federal income tax, self-employment tax, and Connecticut income tax.

This deadline is especially important for sole proprietors, independent contractors, freelancers, partners, and S corporation shareholders whose income is not fully covered by withholding.

Important: Estimated tax rules depend on filing status, business structure, income source, withholding, deductions, credits, prior-year tax, and residency. Use the official instructions for each form or consult a qualified tax professional before making a payment.

1. Determine Whether You Must Pay Estimated Tax!

Federal estimated tax generally applies when both conditions are met:

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

The prior-year percentage increases to 110% when your 2025 adjusted gross income (AGI) exceeded $150,000. The threshold is $75,000 if your filing status is married filing separately.

You may not need federal estimated tax payments if:

You had no federal tax liability for 2025.
You were a U.S. citizen or resident alien for the full year.
Your 2025 tax year covered 12 months.

Use Form 1040-ES, Estimated Tax for Individuals, to project income, deductions, credits, self-employment tax, and required payments. Include business profit from Schedule C, partnership income, S corporation income, investment income, and other taxable amounts.

Reminder: The $1,000 threshold does not eliminate tax liability. It only affects whether an estimated-tax underpayment penalty may apply.

2. Calculate the Federal Safe-Harbor Amount!

The federal safe harbor is based on total payments made through:

Federal income tax withholding.
Estimated tax payments.
Certain refundable credits and other applicable payments.

Use the following tests:

Federal test	Required prepaid amount
Current-year test	At least 90% of 2026 tax
Prior-year test	At least 100% of 2025 tax
Higher-income prior-year test	At least 110% of 2025 tax when 2025 AGI exceeds the applicable threshold

Form 1040-ES generally uses the smaller of the current-year and prior-year amounts to determine the required annual payment. Meeting a safe harbor can prevent an underpayment penalty even if your final 2026 tax is higher.

However, a safe harbor does not eliminate the balance due when the 2026 return is filed. It addresses the timing penalty. You may still owe additional federal tax by the filing deadline.

Warning: Underpayment penalties may be calculated separately for each installment period. Paying the full amount in January does not always eliminate penalties for earlier missed or insufficient installments.

3. Pay the Fourth Federal Installment by January 15, 2027!

For calendar-year taxpayers, the 2026 federal estimated tax schedule is:

April 15, 2026: first payment.
June 15, 2026: second payment.
September 15, 2026: third payment.
January 15, 2027: fourth payment.

The January payment covers the final estimated-tax period of 2026.

Make the payment through an approved method, such as:

IRS Direct Pay
IRS Online Account
Electronic Federal Tax Payment System (EFTPS)
Electronic funds withdrawal during e-filing
Check or money order using the appropriate Form 1040-ES payment voucher

The 2026 Form 1040-ES Payment 4 Voucher is specifically marked “Due Jan. 15, 2027.”

The IRS instructions provide a limited alternative: you generally do not have to make the January 15 payment if you file your 2026 Form 1040 or Form 1040-SR by February 1, 2027, and pay the entire balance due with the return. This alternative does not excuse possible underpayment for the first three periods.

Action: Schedule the federal payment early. Retain the confirmation number, payment date, amount, and account used.

4. Review Connecticut Estimated Tax Requirements!

Connecticut residents and individuals with Connecticut-source income may need to make state estimated tax payments using Form CT-1040ES, 2026 Estimated Connecticut Income Tax Payment Coupon for Individuals.

Connecticut generally requires estimated payments when:

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

For most taxpayers, the Connecticut required annual payment is the lesser of:

90% of the income tax shown on your 2026 Connecticut return, or
100% of the income tax shown on your 2025 Connecticut return, when the 2025 return covered a full 12-month period.

Connecticut’s official Form CT-1040ES instructions do not use the federal 110% higher-income test in the same way. Do not automatically apply the federal 110% rule to your Connecticut calculation.

Connecticut’s 2026 estimated payment dates are:

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

Payments may be made through myconneCT. Electronic payment confirmation should be retained with your tax records.

Partners and S corporation shareholders should include expected distributive or pro rata income. Account for any Connecticut PE Tax Credit expected for 2026.

Warning: Connecticut may charge interest when required payments are not made by the installment dates. Interest may continue even when a refund is ultimately expected.

5. Use the Annualized Income Installment Method for Uneven Cash Flow!

Equal quarterly payments may not reflect how your business actually earns income. A New Haven contractor may receive most revenue in the fourth quarter. A seasonal retailer may earn substantially more in November and December. A consultant may receive a large project payment late in the year.

When income is uneven, complete the annualized income calculations instead of assuming that income was earned equally during all four periods.

For federal purposes:

Complete the 2026 Estimated Tax Worksheet in Form 1040-ES.
Track actual income, deductions, and credits through each required period.
Use the 2026 Annualized Estimated Tax Worksheet, identified as Worksheet 2-9 in IRS Publication 505.
Report the annualized calculation on Form 2210, Underpayment of Estimated Tax by Individuals, Estates, and Trusts.
Complete Schedule AI, Annualized Income Installment Method, when required.

Schedule AI allows required installments to reflect when income was earned. It may reduce or eliminate penalties attributed to earlier periods when the corresponding income had not yet been received.

Connecticut also provides an annualized-income procedure through Form CT-1040ES instructions and related Department of Revenue Services guidance.

Reminder: Keep monthly profit-and-loss statements, bank records, invoices, payment reports, and other documentation supporting the timing of income and expenses.

6. Complete a Year-End Cash-Flow Checklist!

Before January 15, 2027, complete the following steps:

Reconcile business bank and credit-card accounts through December 31, 2026.
Update your year-to-date profit-and-loss statement.
Project fourth-quarter revenue and deductible expenses.
Identify unpaid invoices and expected customer collections.
Record owner draws, distributions, and capital contributions separately.
Calculate federal self-employment tax when applicable.
Review federal withholding from wages, pensions, or other income.
Review Connecticut withholding and expected PE Tax Credits.
Compare total payments with the 90%, 100%, and applicable 110% federal tests.
Determine whether the annualized-income method is appropriate.
Schedule federal and Connecticut payments before January 15.
Save payment confirmations with your 2026 tax records.

Do not use estimated payments to substitute for accurate bookkeeping. Unsupported deductions, unrecorded income, or incorrectly classified transactions can lead to an inaccurate return, processing delays, penalties, and interest.

7. Know Which Forms to Review!

Use these official documents and resources:

Form numbers and instructions may change. Confirm that you are using the documents for the 2026 tax year.

8. Arrange a Professional Q4 Tax Review!

A Q4 estimated-tax review should address more than the payment amount. It should also evaluate projected income, deductible expenses, withholding, entity structure, Connecticut obligations, and the cash required to meet the January deadline.

Jose’s Tax Service provides personalized tax preparation, year-round tax planning, bookkeeping support, federal and Connecticut e-filing, and virtual appointments for New Haven-area and out-of-state clients.

Schedule your tax appointment with ease and review the Small Business Learning Center for bookkeeping, tax, compliance, and business-planning resources.

Deadline reminder: Make required federal and Connecticut fourth-quarter estimated tax payments by January 15, 2027. Late or insufficient payments may lead to underpayment penalties, Connecticut interest, or processing delays.

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