If you're self-employed, a business owner, or have significant income without tax withholding, the IRS generally expects estimated tax payments four times a year rather than one lump sum at filing time.

Estimated payments are typically due in mid-April, June, September, and January of the following year. Because these dates can shift slightly year to year (for weekends and holidays), always confirm the exact date for the current tax year rather than assuming it matches last year's calendar.

Underpaying — or paying late — can trigger an underpayment penalty even if you pay your full balance by the annual filing deadline. Working with your tax planner throughout the year, rather than only at filing time, is the most reliable way to estimate the right payment amount.

Not sure if you should be making estimated payments, or how much to send? That's a conversation worth having before the next deadline, not after.