Quarterly Estimated Tax Calculator for the Self-Employed (2026, Federal + CT)

How quarterly estimated taxes work when you’re self-employed

When you work for an employer, tax comes out of every paycheck. When you work for yourself, nobody withholds for you, so the IRS and the Connecticut Department of Revenue Services expect you to pay as you go through quarterly estimated payments.

Who has to pay

You generally need to make federal estimated payments if you expect to owe at least $1,000 for the year after withholding and credits. Connecticut uses the same $1,000 test for state income tax. Most new freelancers and LLC owners cross that line in their first profitable year.

What you're paying

• Self-employment tax: 15.3% on 92.35% of your net profit, which covers Social Security and Medicare. The Social Security part stops at $184,500 of earnings in 2026.
• Federal income tax: 10% to 37% brackets. Half of your self-employment tax, the $16,100 standard deduction (single, 2026) and the 20% qualified business income (QBI) deduction all lower the income that's taxed.
• Connecticut income tax: rates from 2% to 6.99%. A personal exemption of up to $15,000 (single) phases out as income rises.

2026 due dates

Federal and Connecticut estimates for tax year 2026 are due April 15, June 15 and September 15, 2026, and January 15, 2027. Pay the IRS through IRS Direct Pay or your IRS Online Account. Pay Connecticut through myconneCT.

The safe harbors

You avoid the federal underpayment penalty if you pay the smaller of 90% of this year's tax or 100% of last year's tax (110% if last year's AGI was over $150,000), spread evenly across the four dates. Connecticut's rule is the smaller of 90% of this year's tax or 100% of last year's. If your income jumps, paying based on last year's tax is the simplest way to stay penalty-free. You then settle the rest when you file.

Tips that save headaches

1. Move 25% to 30% of every client payment into a separate tax savings account the day it arrives.
2. Re-run this calculator after each quarter. If income is uneven, the annualized installment method (IRS Form 2210, Schedule AI, and CT Form CT-2210) can lower early payments.
3. Keep receipts organized all year. Every legitimate business expense reduces both self-employment tax and income tax.
4. If you also have a W-2 job, raising your withholding can replace some or all of your estimated payments.

The calculator gives a solid starting estimate. A preparer can fine-tune it with your credits, retirement contributions and prior-year numbers.