Quarterly Estimated Tax Calculator
Self-employment income arrives with no withholding, so the IRS expects you to pay as you go, in four instalments, using Form 1040-ES. Skip them and an underpayment penalty can apply even if you settle the full balance in April.
On $60,000 of net profit, a single filer owes about $12,037 in federal tax for the year — roughly $3,009 each quarter.
How it's calculated
Estimated tax covers both halves of what you owe: self-employment tax and federal income tax on your profit. The calculator above works out the annual figure and divides it into four, which is the right starting point for income that arrives evenly.
The payments are due four times a year — in April, June, and September, and again in January of the following year. The instalments are not quarters of equal length, which surprises people: the second period covers only two months. Payments are made through IRS Direct Pay, EFTPS, or with a mailed 1040-ES voucher.
The safe harbor is the part worth understanding properly, because it converts an uncertain obligation into a fixed one. You avoid the underpayment penalty if you pay at least 90% of the current year's total tax, or 100% of last year's total tax — 110% if your prior-year adjusted gross income was over $150,000. The prior-year route is the one most self-employed people should use, because last year's number is already known and this year's is a forecast. Pay the prior-year amount in four instalments and the penalty is switched off regardless of how much better the year turns out to be.
If your income is genuinely lumpy, there is a second option: the annualised income instalment method, which lets you pay in proportion to what you actually earned in each period rather than in four equal amounts. It requires more record-keeping and Form 2210 Schedule AI at filing time, but it prevents the situation where a strong fourth quarter creates a penalty for the first three.
Two practical notes. If you also have a W-2 job, increasing withholding there is often easier than making estimated payments, and withholding is treated as paid evenly across the year regardless of when it actually happened — which can retroactively fix an underpayment that estimated payments cannot. And most states with an income tax run their own estimated payment system with separate deadlines and penalties.
The reliable habit is to move a percentage of every payment into a separate account as it arrives, rather than trying to find a lump sum four times a year. Our guide to how much to set aside works out the percentage, and the guide to budgeting with irregular income covers the cash-flow side.
A worked example
A freelancer with $60,000 of net profit and no other income owes $8,478 of self-employment tax and $3,559 of federal income tax — $12,037 for the year, or $3,009 per instalment. Suppose their prior-year total federal tax was $9,800 and their prior-year AGI was under $150,000.
Paying four instalments of $2,450 — 100% of last year's tax — switches off the underpayment penalty even though the real liability is $12,037. They will owe the $2,237 difference at filing, but without a penalty, and the certainty is usually worth more than the deferral.
Common mistakes to avoid
- Assuming the payment periods are equal quarters. The second period covers only two months, so a literal quarterly rhythm misses a deadline.
- Estimating this year's income instead of using the prior-year safe harbor. Last year's figure is already known and switches off the penalty regardless of how this year turns out.
- Forgetting the 110% rule. If your prior-year AGI was over $150,000, the safe harbor is 110% of last year's tax rather than 100%.
- Paying the whole balance in April. The penalty is for not paying as you go, so it can apply even when you pay in full at filing.
- Ignoring state estimated payments. Most states with an income tax run their own system with separate deadlines and separate penalties.
Frequently asked questions
When are quarterly estimated taxes due?
Four times a year: in April, June, and September, and again in January of the following year. The periods are not equal quarters — the second covers only two months — so a strict three-month rhythm will miss a deadline. Payments can be made through IRS Direct Pay, EFTPS, or by mailing a Form 1040-ES voucher.
What is the safe harbor rule for estimated taxes?
You avoid the underpayment penalty by paying at least 90% of the current year's tax or 100% of the prior year's total tax, rising to 110% if your prior-year adjusted gross income exceeded $150,000. The prior-year route is the practical choice for self-employed filers, because it relies on a number you already know rather than a forecast of a year still in progress.
What happens if I don't pay quarterly taxes?
An underpayment penalty can apply even if you pay the full balance when you file, because the rule is about paying as you go rather than paying in total. The penalty is calculated per period, so missing early instalments costs more than missing the last one. Meeting a safe harbor removes the penalty regardless of the final balance owed.
Can I pay estimated taxes through payroll withholding instead?
Yes, if you also have a W-2 job, and it is often easier. Withholding is treated as paid evenly throughout the year no matter when it actually occurred, so increasing it late in the year can retroactively cure an underpayment that estimated payments cannot. Ask your employer to adjust your Form W-4 to withhold an additional amount each pay period.
What if my income varies a lot between quarters?
Use the annualised income instalment method, which lets you pay in proportion to what you actually earned in each period instead of in four equal amounts. It requires tracking income by period and completing Schedule AI of Form 2210 at filing, but it prevents a strong final quarter from creating penalties for the earlier ones. The prior-year safe harbor is the simpler alternative if you can fund it.
Sources
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