The US tax system is pay-as-you-go. If you are an employee, withholding handles that quietly in the background. If you are not — or not entirely — the responsibility moves to you.

Who this applies to

You likely need to make estimated payments if you expect to owe a meaningful amount when you file, and your income includes:

  • Self-employment or freelance earnings
  • Distributions from a partnership or S corporation
  • Substantial interest, dividends or capital gains
  • Rental income
  • Retirement distributions without adequate withholding
  • Significant income from a side business alongside a W-2 job

The safe harbour

You do not need to predict your final tax bill perfectly. You need to meet a threshold. Generally, you avoid an underpayment penalty if your payments and withholding for the year total at least:

  • 90% of the tax you end up owing this year, or
  • 100% of last year's total tax — rising to 110% if your prior-year adjusted gross income was above a set threshold

The prior-year figure is the practical one, because it is a number you already know. Take last year's total tax, apply the right percentage, divide by four, and you have a defensible payment schedule — even in a year when your income climbs sharply.

Withholding is treated as paid evenly across the year

This is a genuinely useful quirk. Estimated payments count when you make them, but withholding is treated as though it were spread evenly — whenever it actually occurred. If you reach November underpaid and have a W-2 job or a retirement distribution coming, increasing withholding can retroactively cure an underpayment that a Q4 estimated payment alone would not fix.

The four payment periods

They are not even quarters, which surprises almost everyone the first time:

  1. April 15 — income from January 1 to March 31
  2. June 15 — income from April 1 to May 31 (two months)
  3. September 15 — income from June 1 to August 31 (three months)
  4. January 15 — income from September 1 to December 31 (four months)

How to pay

IRS Direct Pay draws directly from a bank account without a fee. EFTPS suits businesses and anyone who wants scheduled payments set in advance. Card payments work but carry a processing fee. Whichever route you take, keep a record of the date and amount — we need those figures at filing time, and a payment we cannot see is a payment we cannot credit.

Most states run parallel systems with their own vouchers and due dates. If your state has an income tax, budget for both.

Do not forget self-employment tax

People new to self-employment often estimate only income tax and are startled by the final bill. Self-employment tax covers Social Security and Medicare — both halves, since you are employer and employee — and applies to net self-employment earnings on top of income tax. Setting aside 25–30% of net profit is a common starting rule, though the right figure depends on your bracket, deductions and state.

If your income is uneven

Seasonal businesses, a large one-off capital gain, a windfall in a single quarter — the flat quarterly approach can produce a penalty even when the annual total is right. The annualised income method lets you match payments to when income actually arrived. It takes more work, and it is worth it when the timing is genuinely lumpy. Talk to us before the year closes rather than after.