Quarterly Estimated Tax Calculator

If you earn money that doesn't have taxes withheld — moonlighting on a 1099, locums, telehealth, consulting or practice profits — the IRS expects you to pay tax on it during the year, not just in April. This calculator estimates how much to pay each quarter, and the safe-harbor minimum that protects you from penalties.

What this calculator does

Enter your expected 1099 profit, any W-2 wages, the federal tax already withheld from your paychecks, last year's total federal tax, whether last year's AGI was over $150,000, your filing status and your state tax rate. It estimates:

• your total federal tax for the year, including self-employment tax,
• a suggested federal payment for each quarter,
• the safe-harbor minimum per quarter, and
• a rough state payment per quarter.

The formula in plain English

1. Self-employment tax on your 1099 profit: 15.3% on 92.35% of profit, with Social Security stopping once wages plus self-employment earnings reach $184,500 in 2026. A 0.9% Medicare surtax applies above $200,000 (single) or $250,000 (joint).
2. Income tax on W-2 wages plus profit, minus half of the self-employment tax, minus the standard deduction and any QBI deduction you qualify for, using 2026 brackets.
3. Still owed = total tax − withholding. Divide by four for a quarterly payment.
4. Safe harbor = 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), minus withholding, divided by four.

Paying the safe-harbor amount on time means no penalty, even if you owe more when you file.

A worked example

Dr. Kim and her spouse file jointly. She earns $250,000 in W-2 salary with $45,000 withheld, and expects $60,000 of 1099 telehealth profit. Last year their total tax was $55,000, and their AGI was over $150,000. Their state rate is 5%.

• Estimated federal tax this year: about $50,900, including about $2,100 of self-employment tax (she's already past the Social Security wage base, so only Medicare applies).
• Still owed after withholding: about $5,900, or $1,485 a quarter.
• Safe-harbor minimum: just $211 a quarter, because 90% of this year's tax is only slightly above her withholding.
• Rough state payment: about $740 a quarter.

Why it matters at each career stage

If you're: Resident / fellow

If you moonlight on a 1099, set aside about a third of each check. Increasing withholding from your residency paycheck is often the simplest way to cover it.

If you're: Employed

Side income on top of a high salary is taxed at your top bracket. Use safe harbor based on last year's tax to stay penalty-free while you learn what your side income really looks like.

If you're: Practice owner

Practice owners usually owe estimated taxes on profits. If you're an S-corp, much of your income may come through payroll with withholding. Work with your CPA to set payments, and revisit them mid-year if profits change.

How much to set aside from each 1099 payment

If you don't want to run numbers every quarter, a percentage rule works well. Add your federal marginal rate, your state rate and the self-employment tax that applies to you (about 14% if your total earnings are below the Social Security wage base, or about 3% if they're above it). For many clinicians with a W-2 job plus side income, setting aside 35% to 45% of each 1099 payment covers the bill with a little to spare. Any extra becomes a pleasant refund in April.

Tips

Calendar the dates. Set reminders a week before each due date.

Pay online. IRS Direct Pay and your IRS online account are free.

Keep a tax savings account. Move a fixed percentage of every 1099 payment into it as soon as it arrives.

Adjust mid-year. If income changes, recalculate before the next payment.

See how side income adds up with the moonlighting calculator, or compare job types with W-2 vs 1099.