The tax system is pay-as-you-go. Employees satisfy that through withholding without thinking about it. Everyone else has to do it deliberately, four times a year, and the penalty for not doing it is calculated as interest on the shortfall — which means it accrues quietly and is not waived for having filed on time.
Who needs to pay quarterly
Broadly, anyone who expects to owe a meaningful amount when they file and does not have enough tax withheld to cover it. In practice that means:
- Self-employed people and freelancers.
- Owners of partnerships, S corporations and LLCs taking distributions.
- Landlords with profitable rental property.
- Retirees drawing from accounts without withholding elected.
- Anyone with significant investment income, capital gains or crypto activity.
- Employees whose withholding does not keep up with a second income or an equity vest.
The safe harbour
You do not have to predict your tax bill perfectly. The rules provide a safe harbour: pay in at least a set percentage of what you owed last year, or a set percentage of what you owe this year, and the underpayment penalty does not apply. The percentage based on the prior year is higher for taxpayers above an income threshold.
The prior-year route is the one most people should use, because it is a known number rather than a forecast. It is particularly valuable in a year when income is rising: you pay against last year’s smaller figure through the year, and settle the difference when you file.
The quarters are not quarters
The payment periods are uneven, and the due dates are typically April 15, June 15, September 15 and January 15 of the following year. The June payment covers only two months; the January payment covers four. This surprises people who set up equal monthly transfers and assume the timing takes care of itself.
How to work out the amount
The simple version, for a stable year:
- Take last year’s total tax — the tax itself, not the balance you paid on filing.
- Apply the applicable safe-harbour percentage for your income level.
- Subtract any tax you expect to be withheld this year.
- Divide the remainder by four.
For a year with uneven income — a business with a seasonal peak, a one-off capital gain — the annualised income method can reduce or defer payments to match when the income actually arrived. It requires more work at filing, and it is often worth it.
Do not forget the state
Most states with an income tax have their own estimated payment regime, with their own thresholds and, occasionally, their own due dates. Paying federal estimates diligently and ignoring the state is a common and avoidable error.
A practical routine
- Open a separate savings account for tax. Move a fixed percentage of every payment you receive into it on the day it arrives.
- Pay from that account on the due dates, electronically, and keep the confirmation.
- Record each payment somewhere your preparer will see it. Unrecorded estimated payments are one of the most common causes of an incorrect return.
- Revisit the percentage mid-year, particularly if income has moved materially.
If you are not sure whether you need to pay estimates at all, or your income has changed enough that last year’s figure is no longer a useful guide, that is a short conversation with a clear answer. It is worth having in June rather than in April.
This article is general information about how the tax rules work, not tax advice for your situation, and the rules change. Speak with a qualified preparer — we are happy to be that preparer — before acting on anything you read here.