Quarterly Tax Calculator 2026 - Estimated Payments for Self-Employed and Freelancers
As a self-employed worker, you are entirely responsible for calculating and paying taxes four times per year. The formula: Quarterly Payment = (Annual Tax Liability - Withholding) / 4.
Payment Schedule
Q1 (Jan 1 - Mar 31): Due April 15. Q2 (Apr 1 - May 31): Due June 16. Q3 (Jun 1 - Aug 31): Due September 15. Q4 (Sep 1 - Dec 31): Due January 15 (following year).
The Safe Harbor Rule
Option 1: Pay 100% of prior year tax / 4 each quarter (110% if prior year AGI exceeded $150,000). Option 2: Pay 90% of current year estimated tax. Safe harbor = no underpayment penalty regardless of actual tax owed.
The Formula Explained
Step 1: Project annual net SE income. Step 2: SE Tax = Net SE Income x 0.9235 x 0.153. Step 3: AGI = Net SE Income - Half SE Tax - Other deductions. Step 4: Income Tax = bracket math on (AGI - Standard Deduction). Step 5: Total Tax = Income Tax + SE Tax. Step 6: Quarterly Payment = (Total Tax - W-2 Withholding) / 4.
Worked example (Lisa, single freelance writer, $65,000 net SE): SE Tax: $9,188. Half SE deduction: $4,594. AGI: $60,406. Taxable income: $44,656. Income tax: $5,116. Total tax: $14,304. Quarterly payment: $3,576.
| Annual Net SE Income | SE Tax | Income Tax (est.) | Total Annual Tax | Quarterly Payment |
|---|---|---|---|---|
| $30,000 | $4,239 | $1,468 | $5,707 | $1,427 |
| $50,000 | $7,065 | $3,843 | $10,908 | $2,727 |
| $75,000 | $10,598 | $6,396 | $16,994 | $4,249 |
| $100,000 | $14,130 | $10,228 | $24,358 | $6,090 |
| $150,000 | $19,982 | $20,154 | $40,136 | $10,034 |
How to Use This Calculator on CalcAdvisor.com
Calculate your quarterly payments at https://www.calcadvisor.com/calculators/quarterly-tax-calculator.
3 Real-World Examples
Example 1: Lisa, New Freelance Writer
$65,000 projected net SE. Current-year quarterly: $3,576. Prior-year safe harbor (from W-2 job last year): $9,200 / 4 = $2,300. Lisa can safely pay just $2,300/quarter but will owe $5,104 in April. She chooses $3,576 to avoid the April bill.
Example 2: Carlos, Variable Income Developer
Q1 income: $45,000. Q2: $12,000. Q3: $15,000. Q4: $48,000. Total: $120,000. Using annualized income installment method matches payments to actual cash flow: Q1 payment $11,350, Q2 $4,200, Q3 $3,800, Q4 $14,050 - aligning with actual income instead of equal $7,800 quarters.
Example 3: Priya, W-2 Employee With SE Side Income
W-2 withholding: $3,200. Total tax: $28,655. Remaining needed: $25,455. Quarterly: $6,364. She instead requests $2,100/month additional W-4 withholding, converting quarterly obligations into automatic payroll withholding.
Common Mistakes to Avoid
- Treating April 15 as the only tax deadline - missing the June, September, and January payments.
- Calculating quarterly payments based on gross revenue rather than net income.
- Not adjusting quarterly payments when income changes significantly mid-year.
- Ignoring the safe harbor rule and always calculating exact current-year tax.
- Missing the January 15 fourth quarter payment because it falls in the next calendar year.
- Not keeping a separate tax reserve account with 25-30% of every client payment.
- Forgetting state quarterly estimated tax requirements.
Final Thoughts
Calculate your quarterly payments now at https://www.calcadvisor.com/calculators/quarterly-tax-calculator.