Quarterly estimated taxes? Get the right number.

If your tax year is the calendar year, quarterly estimated taxes are due on four dates. April 15 covers January through March. June 15 covers April and May. September 15 covers June through August. January 15 of the next year covers September through December.

So the periods run three months, then two, then three, then four. That surprises a lot of owners, because the word "quarterly" makes them sound equal.

When a due date falls on a Saturday, Sunday or federal holiday, your payment is on time if you make it the next business day. None of the four 2026 dates needed that. January 15, 2028 falls on a Saturday, so that payment can go in the next business day.

This site covers the federal dates only. If your state has an income tax, it may have its own estimated tax dates. If your tax year doesn't end in December, the dates move with your year-end, so that's the first thing we ask.

You can also pay more often than four times. Some owners send a payment every month, which is fine as long as enough has been paid by each due date.

The page on whether quarterly estimated taxes are equal walks through each period in order. For a short list of the dates, see quarterly estimated tax due dates.

You won't owe an underpayment penalty if your withholding and estimated payments add up to the smaller of two amounts. One is 90 percent of this year's tax. The other is 100 percent of the total tax on last year's return.

If last year's adjusted gross income was over $150,000, the last-year amount is 110 percent instead of 100 percent. If you're married and file a separate return, the limit is $75,000.

Most owners start with last year's number because it's already known. You don't have to guess how this year will turn out. Here's a quick example with made-up numbers. Last year's total tax was $20,000 and income was under $150,000, so four payments of $5,000 meet the safe harbor. There's a fuller worked example further down this page.

The 90 percent option makes sense when this year is clearly lower than last year. It depends on accurate books, because you're estimating this year's tax as you go. We use it once your books are up to date and match your bank statements. If this year is different from last year, we tell you. Until your books are caught up, we keep using last year's total tax.

If your income comes in unevenly, there's a third option. The annualized income installment method lets each payment follow the income you've actually earned so far. You figure it on Schedule AI and file Form 2210 with your return.

Some owners give us last year's refund or balance due and call it their tax. Those numbers only show what was left after withholding and payments. The number that counts is total tax, and the page on last year's total tax shows where to find it.

If you're expecting a big year, we're glad to plan for it with you. For the payment itself, we use last year's tax or your up-to-date books, because those are the numbers the safe harbor counts. If neither is ready yet, we start with which date is next and set the amount as soon as the return or the books are in.

You generally have to pay estimated tax if you expect to owe $1,000 or more when you file, after your withholding and refundable credits. That's the IRS rule for individuals, and it covers sole proprietors, freelancers, partners and S corporation shareholders.

The usual reason is income with no tax taken out: business profit, 1099 work, rent, interest, dividends or a gain from selling investments. If all your income is wages and your employer withholds enough, you may never need to send an estimated payment.

A C corporation has its own rule. It generally has to make estimated payments if it expects to owe $500 or more.

There's one more way out. If you had no tax at all last year, were a U.S. citizen or resident for the whole year and last year's return covered 12 months, you don't have to pay estimated tax this year.

Not sure whether you're over the line? Tell us on the call what you earn and what's withheld, and we'll tell you whether you need to pay and how much.

Here's how the math works, with made-up numbers. Dana runs a one-person design business. Last year's total tax on her Form 1040 was $18,400, and her adjusted gross income was $96,000. She has no paycheck, so nothing is withheld.

Because her income was under $150,000, the last-year safe harbor is 100 percent of that tax, or $18,400. That's $4,600 on each of the four dates: April 15, June 15 and September 15, 2026, and January 15, 2027.

This year is going better, and her tax will come to about $26,000. Ninety percent of that is $23,400. The safe harbor is the smaller of the two amounts, so her $18,400 in payments still protects her from a penalty. She'll owe the other $7,600 when she files in April, so we'd help her set money aside for it each month.

If her adjusted gross income last year had been $180,000 with the same tax, she'd need 110 percent, or $20,240. That's $5,060 a payment.

Your numbers will be different. On the free 30-minute call, we do this math with your own return and tell you what to send on your next due date.

Tax taken out of your wages counts toward the same safe harbor as the payments you send yourself. Unless you choose otherwise, the IRS treats one-fourth of your year's withholding as paid on each due date. It doesn't matter which month the tax actually came out of your paycheck.

That means extra withholding late in the year can still help with earlier dates. More tax taken out of a December paycheck can make up for a June payment that came up short.

So before we tell you to send more, we ask about your pay. If you get a paycheck, your year-to-date withholding is a number we can use. We can help you decide how much tax your wages should have taken out. We help set payroll up, and your payroll company runs each payday.

The page on paycheck withholding has more detail. Bring your year-to-date withholding, or tell us you don't get a paycheck. Either answer changes the size of your next payment.

Partnerships and S corporations usually don't make federal estimated income tax payments for the business. The profit passes through to the owners, and each owner makes estimated payments on their own personal return. Two owners means two separate sets of payments, even when the business keeps one set of books.

A C corporation is different. It pays its own estimated tax. For a calendar-year corporation, the due dates are April 15, June 15, September 15 and December 15. That last date comes a month before the personal January date, so owners who mix up the two calendars can miss it.

The page on who pays explains the difference. If you're not sure which kind of return your business files, say so in your note. It's better to sort that out before a due date than after an IRS letter shows up.

Three things are enough to start. First, last year's total tax, or a note that you didn't file last year. Second, the next due date you're facing. Third, if this year looks very different, your books for at least one recent month.

By up-to-date books we mean the month is finished and your accounts match your bank statement. If your bank feed still has uncategorized transactions, or your receipts are in a box, we'll tell you what's left to catch up. Until then, we stay with last year's number.

If you got an IRS notice, send it along. We'll check which due date it's about and go over the penalty with you, using the notice and your payment records.

Send last year's total tax with the form, or book the free 30-minute call and bring your return. If the calendar on that page doesn't load, the form on this page reaches us too.