Morning: Small Business Tax Tips (New Haven): Quarterly Estimated Taxes : Prevent Underpayment Penalties Before January

New Haven, Connecticut : Jose’s Tax Service : September 8, 2026

Small business owners must plan estimated tax payments before income is received, not after the tax year closes. Self-employment income, business profits, rental income, investment income, and other amounts without adequate withholding may create both federal and Connecticut tax obligations.

For calendar-year taxpayers, the next major estimated tax date is January 15, 2027. Review your projected 2026 income now. Confirm your payment history. Adjust your estimate before the final installment becomes due.

This guide explains the federal Form 1040-ES, Estimated Tax for Individuals, and Connecticut Form CT-1040ES, 2026 Estimated Connecticut Income Tax Payment Coupon for Individuals.

Important: This article provides general educational information. Your required payments depend on filing status, income, deductions, credits, withholding, Connecticut residency, business structure, and other individual circumstances.

Who Generally Needs to Pay Estimated Taxes!

Estimated tax payments are commonly required when income is not subject to sufficient withholding.

You may need to make federal estimated 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. You expect your withholding and refundable credits to 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 year.

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

Common situations include:

• Sole proprietors reporting income on Schedule C (Form 1040), Profit or Loss From Business.
• Freelancers, consultants, contractors, and gig workers.
• Partners receiving income through Schedule K-1 (Form 1065).
• S corporation shareholders receiving pass-through income.
• Business owners with substantial investment, rental, or other non-wage income.
• Taxpayers whose wage withholding does not cover both household and business income.

A business entity may have separate tax obligations. An individual owner’s estimated payments generally cover personal federal and Connecticut income tax, including tax attributable to business income. Review entity-level requirements separately.

Connecticut Requirements Under Form CT-1040ES!

Connecticut uses Form CT-1040ES for individual estimated income tax payments.

You generally must make Connecticut estimated payments when:

1. Your expected Connecticut income tax after withholding and any allowable Pass-Through Entity Tax Credit (PE Tax Credit) is $1,000 or more.
2. Your withholding and credits are less than your Connecticut required annual payment.

For 2026, Connecticut’s required annual payment is generally 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 prior-year return covered a full 12-month period.

Connecticut residents, part-year residents, and nonresidents may use different calculations. Nonresidents must account for Connecticut-source income and the applicable apportionment factor.

Review the current Connecticut Department of Revenue Services individual tax information and the official 2026 Form CT-1040ES before submitting a payment.

2026 Federal and Connecticut Payment Deadlines!

For calendar-year taxpayers, federal and Connecticut estimated payments generally follow this schedule:

If a deadline falls on a Saturday, Sunday, or legal holiday, payment is generally due on the next business day.

The January 15, 2027 installment covers the final period of 2026. Do not wait until the filing deadline to address it.

For federal purposes, the January payment may be omitted if you file your 2026 federal return by February 1, 2027, and pay the full balance due with that return. Connecticut has a separate provision in its 2026 instructions. It generally provides relief from underpayment interest when the 2026 Connecticut return is filed by January 31, 2027, and the amount shown as payable is paid in full by that date. Confirm the current state instructions before relying on this exception.

Fiscal-year taxpayers must follow the applicable federal and state fiscal-year schedule. Farmers and fishermen may qualify for special estimated tax rules.

How to Calculate a Practical Safe-Harbor Amount!

Use the following process to establish a working payment amount.

1. Gather prior-year tax figures

Retrieve:

• Your 2025 federal Form 1040 or Form 1040-SR.
• Your 2025 Connecticut Form CT-1040 or Form CT-1040NR/PY.
• Your 2025 estimated payment confirmations.
• Your expected 2026 wage withholding.
• Any expected Connecticut PE Tax Credit.
• Your current year bookkeeping reports.

Use the tax amount required by the applicable instructions. Do not use your refund amount as the safe-harbor figure.

2. Forecast 2026 business income

Estimate:

• Gross receipts.
• Cost of goods sold.
• Ordinary and necessary business expenses.
• Net profit.
• Self-employment tax.
• Retirement contributions.
• Health insurance deductions.
• Qualified business income deductions, if applicable.
• Personal credits and other income.

Update the estimate when revenue changes materially. A January estimate based on outdated sales projections may be insufficient by September.

3. Compare safe-harbor tests

For federal purposes, compare:

• 90% of projected 2026 federal tax, and
• 100% of 2025 federal tax, or 110% for certain higher-income taxpayers.

Example:

• Projected 2026 federal tax: $20,000.
• 90% of projected tax: $18,000.
• 2025 federal tax: $22,000.
• Prior-year safe harbor: $22,000, or $24,200 if the 110% rule applies.

The lower applicable amount may establish the required annual payment. Divide that annual amount into four installments, then subtract any credit from a 2025 overpayment that you applied to 2026.

Connecticut calculations should be completed using the 2026 Estimated Connecticut Income Tax Worksheet included with Form CT-1040ES. Do not simply copy the federal amount. Connecticut modifications, credits, Connecticut-source income, and PE Tax Credits can change the result.

Adjust Payments When Income Is Uneven!

Equal installments are not always appropriate. Seasonal businesses, late-year contracts, capital gains, and irregular distributions can produce uneven income.

If income is concentrated in a particular period:

1. Update your year-to-date profit and loss statement.
2. Recalculate projected federal and Connecticut tax.
3. Review the annualized income installment method.
4. Use federal Publication 505, Tax Withholding and Estimated Tax, when appropriate.
5. Review Connecticut Informational Publication 2018(11), A Guide to Calculating Your Annualized Estimated Income Tax Installments.
6. Use the applicable Connecticut annualized worksheet, including Worksheet CT-1040 AES, when required.

Annualization may reduce an installment for an earlier period when income was not yet earned. It does not eliminate the obligation to document the calculation. Incorrect annualization may lead to underpayment interest.

Use Secure Payment Methods!

For federal payments, use the payment method that produces a reliable confirmation.

Available methods include:

• IRS Online Account.
• IRS Direct Pay.
• Electronic Federal Tax Payment System (EFTPS).
• Electronic funds withdrawal when filing electronically.
• Debit card, credit card, or digital wallet through IRS Payments.
• Check or money order with the correct Form 1040-ES payment voucher.

For Connecticut payments, use myconneCT for electronic payment and confirmation. Connecticut generally permits ACH debit without a payment fee. Card payments may involve a convenience fee.

When mailing a federal payment, use the correct voucher and make the check payable to United States Treasury. For Connecticut, make the check payable to Commissioner of Revenue Services. Enter the correct tax year and identifying information.

A payment submitted without the correct tax year, taxpayer identification number, or voucher may be misapplied and can delay account reconciliation.

Maintain a Complete Payment Record!

Retain the following for every installment:

• Payment date.
• Tax jurisdiction.
• Tax year.
• Amount paid.
• Confirmation number.
• Bank account or card record.
• Copy of the voucher, if mailed.
• Applied prior-year overpayment.
• Calculation supporting the installment.
• Any updated forecast used to change the amount.

Keep federal and Connecticut records in separate folders. Reconcile the records to your tax return before filing.

Avoid These Common Mistakes!

1. Treating business revenue as taxable profit.
   Start with net profit after properly documented business expenses. Then account for self-employment tax and personal income.

2. Using last year’s refund as the payment target.
   A refund reflects withholding, credits, and prior payments. Use the tax liability and applicable safe-harbor figures instead.

3. Ignoring self-employment tax.
   Business owners may owe both income tax and self-employment tax. Excluding either amount can create a substantial balance due.

4. Paying federal tax but not Connecticut tax.
   Federal and state obligations are separate. A federal payment does not satisfy a Connecticut liability.

5. Paying late and assuming a later payment cures the problem.
   Underpayment interest may be calculated separately for each installment. Later payments may not eliminate an earlier-period charge.

6. Failing to update estimates after a profitable quarter.
   Review estimates after major contracts, hiring changes, asset purchases, distributions, or changes in filing status.

7. Relying on an outdated form.
   Use Form 1040-ES for 2026 and Form CT-1040ES for 2026. Incorrect forms can delay processing.

Take Action Before January!

Complete these steps before January 15, 2027:

1. Reconcile 2026 bookkeeping through the latest completed month.
2. Forecast full-year business income and deductions.
3. Review federal Form 1040-ES safe-harbor requirements.
4. Complete the Connecticut Form CT-1040ES worksheet.
5. Confirm prior estimated payments and overpayment credits.
6. Schedule both payments through the official payment portals.
7. Save every confirmation and supporting calculation.
8. Schedule a year-end tax planning review.

Jose’s Tax Service provides year-round tax planning, bookkeeping support, and federal and Connecticut filing assistance for New Haven small businesses, self-employed individuals, and remote clients. Schedule a virtual or in-person tax appointment.

Reminder: Missing a required installment or paying too little may lead to underpayment interest, penalties, or processing delays. Review your circumstances with a qualified tax professional before making a final payment decision.

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