The Complete Guide to Quarterly Estimated Taxes

In a Nutshell

Quarterly estimated taxes are payments you send to the IRS four times a year on income that doesn’t have taxes withheld. For 2026, the deadlines are April 15, June 15, September 15, and January 15, 2027. If you’re a doctor with side income, run a private practice, or work as a locum tenens doc, you probably owe these. Miss them and you’ll face penalties, even if you get a refund at year-end. High earners with AGI over $150K need to pay at least 110% of last year’s tax bill to stay safe. This guide walks you through the dates, the math, and the small mistakes that cost doctors thousands every year.

What Are Quarterly Estimated Taxes?

Quarterly estimated taxes are basically the IRS’s way of getting paid throughout the year instead of waiting until April.

Most W-2 employees never think about this. Their employer pulls taxes from each paycheck automatically. Done.

But when income arrives without withholding, the responsibility shifts to you. The IRS calls this a “pay-as-you-go” system, which sounds friendlier than it really is.

For doctors, this matters more than you’d expect. A hospitalist with a 1099 telemedicine gig on the side. A surgeon who consults for a med-device company. A dermatologist running her own practice. All of them probably need to send quarterly checks.

The payments cover federal income tax, self-employment tax (Social Security and Medicare), and sometimes state tax too if your state has income tax.

Who Needs to Pay Quarterly Taxes?

The IRS rule is pretty simple. If you expect to owe at least $1,000 in tax after withholding and credits, you should be paying quarterly estimated taxes.

In medicine, this hits a lot of people:

• Private practice owners
• Independent contractor physicians (1099 docs)
• Locum tenens doctors
• Physicians with consulting income or expert witness fees
• Doctors with rental property income
• Anyone running an S-corp or partnership in healthcare
• Spouses of physicians who own side businesses

If you’re a W-2 employed physician with no extra income, you’re probably fine. But the moment you start picking up shifts on the side, you’ve stepped into estimated-tax territory.

I think most early-career docs miss this for the first year or two. The first quarterly notice from the IRS is almost always a surprise.

When Are Quarterly Taxes Due?

Here are the 2026 quarterly tax payment deadlines:

• Q1: April 15, 2026 (covers income from January 1 to March 31)
• Q2: June 15, 2026 (covers April 1 to May 31)
• Q3: September 15, 2026 (covers June 1 to August 31)
• Q4: January 15, 2027 (covers September 1 to December 31)

Notice the second quarter only covers two months of income but is due just two months after Q1. The “quarters” aren’t actually equal quarters. Strange, but that’s how the IRS set it up.

If a due date falls on a weekend or federal holiday, the deadline shifts to the next business day.

Understanding the Quarterly Tax Payments Schedule

The quarterly tax payments schedule for self-employed business owners works on a pay-as-you-earn basis.

You earn income in a given period. Then you owe tax on that income shortly after.

For physicians with variable income (think locum tenens or a private practice with seasonal patient flow), this can get messy. A great Q1 followed by a slow Q3 doesn’t even out across the year for IRS purposes. You’re expected to pay tax as the money comes in.

Here’s a quick way to picture it:

• January through March income → pay by April 15
• April through May income → pay by June 15
• June through August income → pay by September 15
• September through December income → pay by January 15

The uneven structure trips up almost everyone the first time.

Quarterly Taxes Dates Every Business Owner Should Know

If you run a private practice or work as a 1099 physician, mark these dates in your calendar. Set reminders a week in advance. Maybe two weeks if you’re the type who needs nudges.

The big four for 2026:

• April 15
• June 15
• September 15
• January 15, 2027

Beyond the federal dates, check your state’s quarterly schedule too. California, New York, and most other income-tax states have their own deadlines that often (but not always) match the federal ones.

For a cardiologist with a Texas-based practice, no state income tax means only the federal dates matter. For a dermatologist in California, you’ll have a separate state payment to send.

Tax Payment Quarterly Dates and IRS Deadlines

The IRS treats these tax payment quarterly dates as hard deadlines. There’s some flexibility but not much.

Pay by midnight on the due date and you’re fine. Pay the next morning and you’re technically late.

If the date lands on a weekend or holiday, you get a one-day extension to the next business day. That’s it.

The IRS sees the postmark date for mailed payments and the electronic confirmation date for online payments. If you mail a check on April 14 but the post office postmarks it April 16, you’re late.

This is why most physicians I’ve talked to just pay online now. It’s faster and the timestamp is instant.

Paying Quarterly Taxes Dates for Self-Employed Workers

For self-employed doctors (think solo private practice, 1099 contractors, locum tenens), paying quarterly taxes dates aren’t optional.

A few things to keep in mind:

• Self-employment tax is 15.3% on top of regular income tax, until you hit the Social Security wage base
• Once you cross that wage base (around $176,100 for 2026), only the 2.9% Medicare portion continues
• High earners pay an extra 0.9% Medicare surtax on income above $200K single or $250K married

That self-employment tax piece is the one that surprises new private practice owners the most. You’re paying both halves of Social Security and Medicare now. The “employer” half doesn’t disappear. It just moves to your side of the ledger.

Dates to Pay Quarterly Taxes Without Missing Deadlines

The cleanest way to avoid missing dates to pay quarterly taxes is to automate.

A few practical options:

• Set calendar alerts 10 days before each deadline
• Use the IRS Direct Pay system to schedule payments in advance
• Have your CPA send a reminder email or invoice
• Move money to a separate “tax savings” account every time you get paid

That last one is the trick a lot of high-income docs swear by. Every time a payment hits your business account, transfer 30 to 40 percent into a tax savings account. When the deadline arrives, the money is sitting there waiting.

I’ve seen physicians try to “catch up” at year-end and it almost never goes well.

How to Calculate Quarterly Estimated Taxes

Calculating quarterly estimated taxes isn’t as scary as people make it sound. There are two main approaches.

Method 1: Safe Harbor (the easy way)

Take your total tax bill from last year. If your AGI was over $150K (which most physicians will hit), pay 110% of last year’s tax in four equal installments. That’s it. You’re safe from penalties no matter what happens this year.

Example: A radiologist owed $180,000 in federal tax last year. To use safe harbor, she needs to pay $198,000 this year (110% of $180K), or $49,500 per quarter.

Method 2: Annualized Income (the precise way)

Project your current-year income, deductions, and tax bill. Pay 90% of that across four installments. Better if your income fluctuates a lot.

For most high-income medical professionals, safe harbor is simpler and worth the extra cost. You’d rather overpay a bit and get a refund than underpay and owe penalties.

Form 1040-ES has worksheets to help with the math. Or you can just ask your CPA to send you vouchers each quarter.

Safe Harbor Rules and Quarterly Tax Penalties

Safe harbor is the key concept every high-income earner should understand.

If your AGI is under $150K, you avoid penalties by paying:

• 90% of this year’s tax, OR
• 100% of last year’s tax

If your AGI is over $150K (the situation for almost every physician), you avoid penalties by paying:

• 90% of this year’s tax, OR
• 110% of last year’s tax

The 110% rule is easier because you already know last year’s number. No guessing.

If you miss safe harbor, the IRS calculates an underpayment penalty based on the federal short-term rate plus 3%. As of mid-2026, that’s hovering around 7 to 8% annualized. Not catastrophic, but not nothing either.

For a surgeon who underpays by $50,000 for half the year, that’s roughly $1,750 in penalties. Money you didn’t need to lose.

How to Pay Quarterly Taxes Online

Paying quarterly taxes online is the simplest option, and the IRS now has several good ways to do it.

Top three options:

1. IRS Direct Pay — Free, links to your bank account, no signup required
2. EFTPS (Electronic Federal Tax Payment System) — Requires enrollment but lets you schedule payments up to a year in advance
3. Debit or credit card through an IRS-approved processor — Convenient but charges a fee (usually around 1.85% for credit cards)

For most physicians, EFTPS or Direct Pay is the way to go. EFTPS is what I’d lean toward if you want set-and-forget scheduling.

You can also pay through your tax software (TurboTax, H&R Block, and others) or through the IRS2Go mobile app.

After you pay, save the confirmation number somewhere safe. Your CPA will need it at year-end.

Common Quarterly Tax Mistakes

A few mistakes I see over and over with medical professionals:

• Underestimating self-employment tax. That 15.3% adds up fast on $300K of 1099 income.
• Forgetting state quarterly payments. Federal isn’t the only one.
• Treating all income equally. Capital gains, dividends, and 1099 income all interact differently.
• Not adjusting after a big year. If your bonus was huge, the next quarterly might need to be bigger too.
• Waiting until the deadline. The IRS website tends to slow down on April 15.
• Skipping a quarter because cash flow was tight. The penalty doesn’t care about your cash flow.
• Mixing personal and business funds. Makes the math harder later.

Honestly, the biggest mistake is just ignoring it. The IRS is patient but persistent. They will get their money, with interest.

Quarterly Tax Strategies for High-Income Earners

For physicians making serious money, a few strategies tend to help.

Increase W-2 withholding to cover 1099 income

If you have both W-2 and 1099 income, you can ask your hospital employer to withhold extra federal tax from your paycheck. W-2 withholding is treated as if it was paid evenly throughout the year, which can rescue you from earlier underpayments.

Use retirement contributions to reduce taxable income

A solo 401(k), SEP-IRA, or cash balance plan can shelter big chunks of income. A solo 401(k) lets you put away up to $70,000 in 2026 (more if you’re over 50). A cash balance plan can shelter several hundred thousand more if your income supports it.

Track deductible expenses religiously

CME, malpractice insurance, professional licensing, medical equipment, home office expenses for telemedicine work. These add up fast for a practice owner.

Consider an S-corp election

If you’re earning $300K-plus as a 1099 contractor, an S-corp election can save significant self-employment tax. You pay yourself a reasonable salary, then take the rest as distributions. The math gets complicated, so this is one to discuss with a CPA before pulling the trigger.

Pay quarterly with a buffer

Most high-income docs pay slightly more each quarter than required. The peace of mind is worth more than the small opportunity cost.

Frequently Asked Questions

What Happens If I Miss a Quarterly Tax Payment?

If you miss a quarterly tax payment, the IRS charges an underpayment penalty starting from the missed deadline. The penalty rate is the federal short-term rate plus 3%, calculated daily. For 2026, that’s roughly 7 to 8% annualized.

You can still pay late and stop the penalty from growing, but you can’t undo the days you missed. The faster you pay, the smaller the bill.

A missed quarterly tax payment doesn’t go on your credit report or anything dramatic. The IRS just adds the penalty to your year-end return. Form 2210 calculates it for you.

When Are Quarterly Taxes Due?

When are quarterly taxes due for 2026? The quarterly taxes dates are April 15, 2026, June 15, 2026, September 15, 2026, and January 15, 2027. These are the four estimated tax deadlines you need to remember.

If any of those dates fall on a weekend or holiday, the deadline shifts to the next business day.

How Do I Pay Quarterly Taxes?

You can pay quarterly taxes online through IRS Direct Pay, EFTPS, the IRS2Go app, or a credit or debit card via an IRS-approved processor.

You can also mail a check with Form 1040-ES voucher, but most physicians find paying quarterly taxes dates much easier to manage online. Online payments are timestamped immediately and there’s no risk of mail delays.

Do I Need to Pay Quarterly Taxes?

If you expect to owe at least $1,000 in tax after withholding and credits, you probably need to pay quarterly estimated taxes. Who needs quarterly taxes the most? Self-employed physicians, private practice owners, locum tenens doctors, 1099 contractors, and physicians with substantial side income from consulting or rental properties.

If you’re purely a W-2 employed physician with no other income sources, you can probably skip quarterly payments and let your paycheck withholding handle everything.

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If you’re a doctor staring down your first big quarterly payment, or just want a second set of eyes on your tax strategy, talk to a CPA who works specifically with medical professionals. The complexity of physician compensation (W-2 plus 1099 plus partnership distributions plus capital gains) is worth a real expert’s time. A 30-minute conversation now could save you thousands at year-end.

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