# Quarterly Estimated Tax Calculator for Self-Employed Contractors (2026)

Quarterly estimated tax is the federal income and self-employment tax you prepay four times a year when no employer withholds it. For 2026, pay the smaller of 90% of this year's tax or 100% of last year's (110% if last year's AGI topped $150,000), split across April 15, 2026, June 15, 2026, Sept. 15, 2026 and Jan. 15, 2027.

## Key takeaways

- You generally must pay estimated tax if you expect to owe $1,000 or more after withholding.
- The safe harbor is the smaller of 90% of 2026 tax or 100% of 2025 tax (110% if 2025 AGI was over $150,000, $75,000 married filing separately).
- 2026 due dates: April 15, 2026, June 15, 2026, Sept. 15, 2026, Jan. 15, 2027.
- Self-employment tax (15.3% on most profit) is part of the estimate, not a separate bill.
- This calculator is federal only. Most states with an income tax have their own estimated payments.

> **Estimate, not tax advice**
>
> This tool estimates federal tax using 2026 IRS figures (standard deduction, rate schedules, self-employment tax and the QBI deduction below its threshold). It does not include credits, itemized deductions, state tax, or newer deductions such as those for tips, overtime or seniors. Use it to plan, then confirm your payments with a CPA or enrolled agent.

## How do you calculate quarterly estimated taxes?

Estimate this year's total federal tax, compare 90% of it with 100% (or 110%) of last year's total tax, take the smaller number, subtract any withholding, and divide by four. That's the method on the 2026 [Form 1040-ES](https://www.irs.gov/pub/irs-pdf/f1040es.pdf) worksheet, and it's what the calculator does.

**Formula**

```
Payment per quarter = (min(90% × T₍this year₎, P × T₍last year₎) − W) ÷ 4
```

Where:
- T₍this year₎ = estimated 2026 total tax: income tax + self-employment tax + Additional Medicare Tax
- T₍last year₎ = total tax shown on your 2025 return
- P = 100%, or 110% if your 2025 AGI was over $150,000 ($75,000 if married filing separately)
- W = federal income tax withheld from W-2 wages during 2026

1. **Project your net profit for the year.** Take revenue minus business expenses so far, then scale it to twelve months. If your work is seasonal, use last year's month-by-month split instead of a straight line.
2. **Figure self-employment tax.** Multiply profit by 92.35%, then by 15.3% (12.4% Social Security up to the $184,500 wage base, plus 2.9% Medicare). Half of it is deductible. The [self-employment tax calculator](https://www.brix.so/tools/self-employment-tax-calculator) breaks this out.
3. **Figure income tax.** Subtract half of SE tax and the 2026 standard deduction ($16,100 single, $32,200 married filing jointly), take the 20% [QBI deduction](https://www.brix.so/learn/qbi-deduction) if you qualify, and run the rest through the 2026 brackets.
4. **Pick your safe harbor.** Compare 90% of that total with 100% or 110% of last year's tax. The smaller number is the least you can prepay without an underpayment penalty.
5. **Pay a quarter by each due date.** Pay through IRS Direct Pay, EFTPS or your IRS online account by April 15, 2026, June 15, 2026, Sept. 15, 2026, Jan. 15, 2027.

> **Worked example**
>
> A single HVAC owner expects $120,000 of net profit in 2026 and has no W-2 job. Last year's return showed $24,000 of total tax on $105,000 of AGI.
>
> Self-employment tax is $16,955. After half of it and the $16,100 standard deduction, taxable income is $95,422; the QBI deduction of $19,084 brings it to $76,338, for $11,506 of income tax.
>
> Estimated 2026 total: $28,462. 90% of that is $25,616; 100% of last year is $24,000. The prior-year number is smaller, so the owner pays **$6,000 a quarter** and owes about $4,462 more at filing time, penalty-free.
>
> About 24% of profit goes to federal tax here. State tax comes on top.

## When are 2026 quarterly estimated taxes due?

For calendar-year taxpayers, the 2026 payments are due April 15, 2026, June 15, 2026, Sept. 15, 2026 and Jan. 15, 2027. The "quarters" aren't equal: the second payment comes only two months after the first. A payment mailed with a U.S. postmark on or before the due date counts as on time.

**2026 federal estimated tax due dates**

| Payment | Due date | Worked example amount |
| --- | --- | --- |
| 1st payment | April 15, 2026 | $6,000 |
| 2nd payment | June 15, 2026 | $6,000 |
| 3rd payment | Sept. 15, 2026 | $6,000 |
| 4th payment | Jan. 15, 2027 | $6,000 |

_Source: IRS Form 1040-ES (2026). You can skip the Jan. 15, 2027 payment if you file your 2026 return by Feb. 1, 2027 and pay the full balance with it._

## What is the safe harbor for estimated taxes?

The safe harbor is the smallest prepayment that keeps you clear of the IRS underpayment penalty: 90% of this year's tax or 100% of last year's, whichever is less. If your 2025 adjusted gross income was over $150,000 ($75,000 married filing separately), the prior-year number is 110%. Your 2025 return must cover a full 12 months.

- **Prior-year safe harbor** is the one most owners use. It's a fixed number you know in April, so a big year can't surprise you with a penalty. You still owe the difference when you file.
- **Current-year safe harbor** (90%) saves cash when this year is slower than last, but it only works if your estimate holds up. Recheck it every quarter.
- **High-income rule.** With the same $120,000 profit, an owner whose 2025 AGI was $160,000 and tax was $30,000 would have a 110% target of $33,000. That's higher than 90% of this year ($25,616), so the 90% route wins at $6,404 a quarter.
- **No tax last year.** If you were a U.S. citizen or resident for all of 2025 and had no tax liability for that full year, you generally don't have to pay 2026 estimated tax.

## How much should a contractor set aside for taxes?

A useful habit is to move a fixed share of every customer payment into a separate tax account. The calculator's "share of profit to set aside" shows your number; in the example it's 24% of profit for federal tax alone. Add your state's rate on top. See [how much to set aside for taxes](https://www.brix.so/learn/how-much-to-set-aside-for-taxes) for a fuller walkthrough.

**What changes your estimate**

| Situation | What to do |
| --- | --- |
| Seasonal trade (roofing, landscaping, pool, snow) | Most profit lands in a few months. The annualized income installment method (Form 2210, Schedule AI) can let you pay less early in the year. |
| You bought a truck or equipment | A [Section 179](https://www.brix.so/tools/section-179-calculator) or bonus depreciation deduction can cut this year's tax. Lower your current-year estimate once the purchase is placed in service. |
| You also have a W-2 job or a working spouse | Withholding counts as paid evenly through the year. Raising W-4 withholding can replace estimated payments. |
| Profit is well above last year | The prior-year safe harbor still protects you from the penalty, but a big balance comes due at filing. Save the difference. |
| Taxable income above $201,750 (single) | The QBI deduction starts to phase down. The calculator leaves it out above the threshold, so your real tax may be lower. |

## What happens if you miss or underpay a quarter?

The IRS charges an underpayment penalty figured like interest, for each quarter, from the due date until the shortfall is paid. Paying a missed quarter late still cuts the penalty, so pay as soon as you can rather than waiting for April. You may be able to reduce it with the annualized method if your income was uneven.

## Common mistakes

- **Forgetting self-employment tax.** Income tax alone understates what a sole proprietor owes, often by thousands.
- **Using revenue instead of profit.** Estimated tax is figured on net profit after business expenses, not on what customers paid you.
- **Spending the tax money.** Cash in the operating account looks like profit until June 15 shows up.
- **Skipping state estimates.** Most income-tax states have their own quarterly schedule. See your state in our [state tax guides](https://www.brix.so/guides/contractor-taxes).
- **Messy books.** If expenses aren't categorized monthly, you can't project profit, so every estimate is a guess. A monthly [bookkeeping checklist](https://www.brix.so/learn/bookkeeping-checklist-for-contractors) fixes that.

BRIX keeps your expenses categorized and synced with QuickBooks so your profit number is current, and reminds you before each quarterly estimated tax date. BRIX doesn't file taxes or give tax advice; your CPA still signs off on the numbers.

- [Bookkeeping and tax help](https://www.brix.so/features/bookkeeping-taxes): Keeps expenses categorized, tracks 1099 subcontractors and sales tax, and reminds you of quarterly estimated tax dates. BRIX does not file taxes or give tax advice.
- [QuickBooks sync](https://www.brix.so/integrations/quickbooks): Syncs customers, invoices and payments with QuickBooks so the books match the jobs.

## Frequently asked questions

### When are 2026 estimated tax payments due?

April 15, 2026, June 15, 2026, Sept. 15, 2026 and Jan. 15, 2027, according to the 2026 Form 1040-ES. If you file your 2026 return by Feb. 1, 2027 and pay everything owed, you can skip the January payment.

### Do I have to pay quarterly taxes if I'm self-employed?

Generally yes, if you expect to owe at least $1,000 in federal tax after withholding and refundable credits. Most contractors with a profitable business clear that line easily, because self-employment tax alone is about 14% of profit.

### How is quarterly estimated tax calculated?

Estimate your total 2026 tax (income tax plus self-employment tax), compare 90% of it with 100% of last year's total tax (110% if last year's AGI was over $150,000), take the smaller amount, subtract withholding, and divide by four.

### What percentage of my income should I set aside for taxes?

It depends on your profit, filing status and state. In this page's example, a single owner with $120,000 of profit owes about 24% of it in federal tax. Run your own numbers in the calculator and add your state income tax rate.

### Can I pay all my estimated taxes at once?

Yes. You can pay the whole year's estimate by the first due date, April 15, 2026. Paying late in the year doesn't fix earlier quarters, though, because the penalty is figured quarter by quarter.

### What if my income changes during the year?

Rerun the estimate and adjust the remaining payments. If you use the prior-year safe harbor, your required payments don't change, but you should save for the larger balance due at filing.

### Does this calculator include state estimated taxes?

No. It covers federal income tax, self-employment tax and Additional Medicare Tax only. Check your state revenue department for its own estimated tax rules and due dates.

## Related

- [Quarterly Estimated Taxes for Contractors: How They Work in 2026](https://www.brix.so/learn/quarterly-estimated-taxes-for-contractors)
- [How Much Should You Set Aside for Taxes When You're Self-Employed?](https://www.brix.so/learn/how-much-to-set-aside-for-taxes)
- [Self-Employment Tax Calculator (2026)](https://www.brix.so/tools/self-employment-tax-calculator)
- [What Is Self-Employment Tax?](https://www.brix.so/learn/self-employment-tax)
- [What Is the QBI Deduction?](https://www.brix.so/learn/qbi-deduction)
- [Section 179 Calculator for Trucks, Vans and Equipment (2026)](https://www.brix.so/tools/section-179-calculator)
- [Taxes for Contractors: The 2026 Guide for Self-Employed Trades Owners](https://www.brix.so/guides/contractor-taxes)
- [Bookkeeping for contractors that keeps your books tax-ready all year](https://www.brix.so/features/bookkeeping-taxes)
- [Mileage Deduction Calculator for Contractors (2026)](https://www.brix.so/tools/mileage-deduction-calculator)
- [What Is the Section 179 Deduction?](https://www.brix.so/learn/section-179-deduction)

## Sources

- [IRS Form 1040-ES (2026), Estimated Tax for Individuals](https://www.irs.gov/pub/irs-pdf/f1040es.pdf) (checked 2026-10-12)
- [IRS Rev. Proc. 2025-32, 2026 inflation adjustments](https://www.irs.gov/pub/irs-drop/rp-25-32.pdf) (checked 2026-10-12)
- [IRS Topic No. 554, Self-Employment Tax](https://www.irs.gov/taxtopics/tc554) (checked 2026-10-12)
- [IRS Topic No. 751, Social Security and Medicare Withholding Rates](https://www.irs.gov/taxtopics/tc751) (checked 2026-10-12)
- [IRS Topic No. 560, Additional Medicare Tax](https://www.irs.gov/taxtopics/tc560) (checked 2026-10-12)
- [IRS, Qualified business income deduction](https://www.irs.gov/newsroom/qualified-business-income-deduction) (checked 2026-10-12)

---
Written by BRIX Editorial Team. Last updated 2026-10-12. General information, not tax, legal or financial advice.
Canonical: https://www.brix.so/tools/quarterly-estimated-tax-calculator