Quarterly estimated taxes for self-employed contractors

Your first full year on your own goes well. Then you file in April, the return says you owe five figures, and underneath it there is a penalty for not having paid any of it during the year. Nothing went wrong with the business. Nobody was withholding.

The IRS treats income tax as pay-as-you-go. It wants the money roughly as you earn it, not in one payment the following spring.

General business guidance, not tax advice. Rules and figures change. Verify anything specific against the current Form 1040-ES instructions, IRS Publication 505, or a CPA who works with contractors.

Nobody is withholding, so two taxes stack

An employee has income tax, Social Security and Medicare taken out of every check, and the employer pays half of the Social Security and Medicare. Working for yourself, you owe both halves. That is self-employment tax, and it sits on top of ordinary income tax on the same profit.

The self-employment tax rate is 15.3% — 12.4% Social Security plus 2.9% Medicare. Schedule SE applies it to 92.35% of net profit, not the whole number. The Social Security half stops at an annual wage base ($184,500 for 2026, reset every year). The Medicare half is uncapped, and an extra Medicare surtax kicks in at higher incomes.

If you are a sole proprietor or a single-member LLC, estimated payments are personal. They go under your Social Security number against your Form 1040, not under the business EIN. If you elected S corporation treatment, some of your income should be coming through payroll with real withholding, which changes the arithmetic — ask your accountant.

A 1099-NEC is the form a business files to report what it paid you, and none of that money had tax taken out of it. Neither did the checks from homeowners, who never file a 1099 at all.

The four dates are not quarters

This is the part that catches people. The periods are uneven, and only the first is a real calendar quarter.

Those are the IRS's own payment periods. The second is two months long. The fourth is four months and lands after New Year. Set reminders for the ends of March, June, September and December and three of the four will be wrong.

A due date that lands on a weekend or legal holiday moves to the next business day, so read the current year's four off IRS.gov each January and put those in your phone. You may also skip the January installment if you file the return and pay the whole balance by January 31 — a date that shifts the same way.

Pay through your IRS Online Account, Direct Pay, or EFTPS, which needs enrolling ahead of time. Mailed 1040-ES vouchers still work. Save every confirmation: the return asks for all four amounts and dates.

The safe harbor is the trick worth learning

You do not have to predict this year's tax correctly. You have to pay enough to land inside a safe harbor, and then whatever you actually owe is settled at filing without a penalty.

Per the Form 2210 instructions and IRS Topic 306, you generally avoid the underpayment penalty if your payments and withholding reach the smaller of:

• 90% of the tax you end up owing this year, or
• 100% of the tax shown on last year's return — 110% if last year's adjusted gross income was over $150,000 ($75,000 if you file married filing separately).

There is a small-balance exception too: no penalty if your total tax minus withholding and refundable credits comes to less than $1,000. That test looks at withholding, not at estimated payments you made.

With a prior-year return in hand, the safest payment is arithmetic instead of forecasting. Take the total tax line from last year, apply 100% or 110%, divide by four, pay that. A boom year does not break it: you owe the difference in April, penalty-free.

Sizing it in a year with no prior return

First year out there is no prior-year number to lean on, so you estimate. Reserve a percentage of net profit as you go, and pay the reserve out each period.

The $5,250 is the April payment. Note what the reserve is calculated on: profit, not deposits. Reserving against gross revenue is the common mistake — 30% of the $42,000 collected is $12,600, and the gap widens the more materials you buy.

The 30% is a placeholder, not a rule. Your real percentage depends on filing status, a spouse's income and withholding, your deductions, and whether your state taxes the profit too. Run the Estimated Tax Worksheet in the Form 1040-ES package once, or have a CPA run it, and use a number that is actually yours. Then keep the reserve in a separate account.

When the year is lopsided

Seasonal trades do not earn in four equal pieces. A landscaper bills most of the year between May and September, so a flat quarter of an annual estimate in April is money that has not come in yet.

There is a method for this. The annualized income installment method — Schedule AI of Form 2210 — matches each required payment to the income actually earned in that period, so a thin winter installment is not automatically an underpayment. It takes real quarter-by-quarter bookkeeping, and is worth having prepared for you the first time.

There is also a lever people miss. If you or a spouse has W-2 wages anywhere, tax withheld from those wages is by default treated as paid in equal parts across the year, whenever it was actually taken — see the withholding chapter of Publication 505. Raising that withholding in the autumn can therefore cover a shortfall from earlier in the year in a way a December estimated payment cannot.

If you miss one, pay it late anyway

The underpayment charge is not a fine. It works like interest. It runs on the shortfall from the day the installment was due until the day you pay it or the April filing deadline, whichever comes first, at a rate the IRS resets each quarter.

Because it adds up by the day, paying the moment you notice costs less than waiting for April. And do not skip the next one because the last one slipped.

If the total is genuinely unaffordable, file the return on time anyway and look at an IRS payment plan. The failure-to-file penalty runs at a much higher monthly rate than the failure-to-pay penalty, so not filing is a far more expensive problem than not paying.

Your state runs a separate calendar

Most states with an income tax run their own estimated-tax system, often on similar dates but with their own forms, thresholds and safe-harbor rules. A handful of states have no individual income tax at all. Check your state revenue department directly rather than assuming the federal dates carry over.

Where the revenue number comes from

Every method above starts with knowing what you billed in a specific stretch of weeks. Keep your estimates and approvals in DoneQuote and each accepted job is dated and priced in one place, so sizing the June payment means filtering April and May instead of rebuilding them from your phone. It will not calculate your tax. It answers the question the worksheet asks first.