Quarterly Estimated Tax Deadlines Every Small Firm Owner Should Know

You spend your working hours helping clients stay ahead of their own deadlines. It's easy to let your own firm's quarterly estimated taxes become the thing you handle at the last minute. Here's the schedule and the math, kept simple enough to actually use.

Who has to pay quarterly

If you're a sole proprietor, single-member LLC, partner, or S-corp shareholder and you expect to owe $1,000 or more in tax for the year after subtracting withholding and credits, the IRS expects you to pay estimated tax in quarterly installments rather than one lump sum at filing time. Most solo practitioners and small-firm owners fall into this category the moment they stop drawing a W-2 paycheck with tax withheld.

The four deadlines

Estimated tax is paid in four installments tied to the income period, not evenly spaced calendar quarters. For a calendar-year filer, the standard due dates are April 15, June 15, September 15, and January 15 of the following year, shifted to the next business day if any of those fall on a weekend or holiday. The exact current-year dates and payment vouchers are published on the IRS's Form 1040-ES page, worth bookmarking since the dates can shift slightly year to year.

A simple way to estimate what you owe

The most reliable shortcut for most firm owners is the safe-harbor rule: if you pay in, through withholding and estimated payments combined, at least 100% of last year's total tax liability (110% if last year's adjusted gross income was over $150,000), the IRS generally won't assess an underpayment penalty, even if you end up owing more when you file. Take last year's total tax owed, divide by four, and that's a defensible quarterly number if your income is roughly similar or growing. If your income jumped significantly, paying based on 90% of this year's actual projected liability is the more precise (if more work) alternative.

What happens if you miss one

Missing or underpaying a quarter doesn't wait until filing season to catch up with you; the IRS calculates a penalty for each period a payment was late or short, using a rate tied to the federal short-term rate plus 3%. Catching up the following quarter reduces the penalty going forward but doesn't erase what accrued. If you've missed a payment, the fix is to pay the shortfall as soon as possible rather than waiting for the next scheduled date.

Where to actually pay

IRS Direct Pay (free, from a bank account) and EFTPS (free, requires enrollment in advance) are the two most reliable methods; both are linked from the Form 1040-ES page above. Paying by mailed check with a 1040-ES voucher still works but adds mail-time risk to a hard deadline.