Estimated Tax Payment Calculator

Withholding already covers part of the year\u2019s liability

Expected income of $90,000 at an 18% effective rate implies $16,200 of tax. With $6,000 already being withheld, $10,200 remains, which across four quarters is $2,550 each. Ignoring the withholding and dividing the full liability by four would over-pay by $1,500 a quarter.

Getting this right matters in both directions. Under-paying triggers a penalty in most systems, charged as interest from the date each instalment was due rather than from the filing deadline. Over-paying hands the tax authority an interest-free loan for up to a year and a half.

Pay last year\u2019s liability and the penalty generally does not apply

Forecasting a year accurately is difficult for anyone with variable income, and most systems provide a safe harbour precisely for that. Paying at least the previous year\u2019s total liability — or a slightly higher multiple of it for higher earners — generally avoids the underpayment penalty however the current year turns out.

This is usually easier to satisfy than an accurate forecast, because last year\u2019s figure is a known number on a filed return. It is the standard advice for anyone whose income is lumpy: pay the safe harbour amount in equal instalments, and settle any genuine excess at filing.

Anyone whose income arrives without tax deducted

Employment income has tax withheld at source. Self-employment, freelance work, rental income, investment income, capital gains and most one-off receipts do not. Where enough income arrives un-withheld, estimated payments become a requirement rather than an option, usually above a modest threshold of tax owed.

There is an alternative worth knowing: someone with both employment and side income can often increase withholding on the salary instead of making separate instalments. In several systems withholding is treated as paid evenly across the year regardless of when it was deducted, which makes it a way to fix an underpayment late in the year without a penalty.

Income arriving evenly, which self-employed income rarely does

Dividing the remaining liability into four equal instalments assumes income accrues evenly through the year. A business earning most of its income in one quarter may over-pay early and strain cash flow. Most systems allow an annualised-income method that matches instalments to when income was actually earned, at the cost of more paperwork.

The effective rate entered also has to be realistic. It should include self-employment or social contributions where they apply, not just income tax — for self-employed income those contributions are frequently the larger half of the bill, and an estimate built on income tax alone will fall substantially short.

Sources & References

Figures on this page are checked against primary, authoritative sources. Links open in a new tab.

• Estimated taxes — Form 1040-ES; estimated tax is generally paid in four installments, and the safe harbor avoids an underpayment penalty by paying at least 90% of the current year’s tax or 100% of the prior year’s tax (110% for higher-income taxpayers)Internal Revenue Service · verified 2026-06-05

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