How do quarterly estimated payments actually work?

The US tax system is pay-as-you-go. If you run a business, you cannot wait until April 15 to pay all the tax you owe. The IRS expects you to pay throughout the year, and they charge penalties if you wait too long, even if you pay everything you owe by the filing deadline.

Estimated payments are due four times a year. April 15 covers income earned January through March, June 15 covers April and May, September 15 covers June through August, and January 15 of the following year covers September through December. These dates apply to both federal and most state estimated payments.

The penalty catches people off guard. You might think you’ll just pay the full balance when you file in April. The problem is the IRS charges a penalty for each quarter you underpaid, calculated like interest on the amount you should have paid. So even if you write a check for everything you owe on April 15, you still owe penalties for not paying during the year. The penalty rate changes periodically and has been running around 8% annually, though current rates should be verified with the IRS.

Safe harbor rules make the amounts predictable. You can avoid penalties entirely by paying at least 100% of last year’s tax liability spread across the four quarterly payments. If your adjusted gross income was above $150,000, the threshold is 110% of last year’s tax. This means you don’t have to guess what your current year’s profit will be. Look at last year’s total tax, divide by four, and pay that amount each quarter. If you end up owing more at filing time, you pay the balance without penalties because you met safe harbor.

For clinicians who work a W-2 job alongside their business, there’s another useful strategy. You can increase the withholding on your W-2 paycheck to cover the tax on your business income. W-2 withholding is treated as if it were paid evenly throughout the year, even if you increase it in December. So if you realize in October that your business had a strong year and you’re behind on estimates, bumping up your W-2 withholding for the rest of the year can catch you up without quarterly payment penalties. This applies to many medical business owners who earn W-2 income at their clinical job while running a practice or agency on the side.

Hunter Green CPA calculates estimated payment amounts and schedules them as part of ongoing tax work for medical business owners nationwide. The Bookkeeping and Tax Package bundles monthly bookkeeping with tax return preparation and includes this planning, since clean books make accurate estimates possible. When the books are current all year, the estimated payments reflect what is actually happening in the business.

If you’re unsure what you should be paying or whether your current approach is right, book a consultation to review your situation.