Estimated Taxes for Small Business: 2026 Deadlines

The US tax system runs on pay-as-you-go. An employee has tax pulled out of every paycheck through withholding. A business owner, freelancer, or anyone with income that is not subject to withholding does not get that automatic mechanism, so the IRS requires them to send in the equivalent amount themselves, four times a year, in the form of estimated tax payments.

This applies to a sole proprietor filing Schedule C, a partner in an LLC or partnership, an S-corporation shareholder reporting their share of profit on a K-1, and a C-corporation itself as a separate taxpayer. The rule of thumb for an individual: if you expect to owe $1,000 or more in tax for the year after subtracting withholding and refundable credits, you are on the hook for estimated payments. For a C-corporation, the threshold is lower in practical terms, generally any corporation expecting to owe $500 or more.

Missing this is not the same as missing a filing deadline. Nothing stops you from filing your return on time in April. What happens instead is that the IRS charges an underpayment amount, calculated like interest, on the gap between what you should have paid during the year and what you actually paid, for the period the money was not with the IRS.

For an individual, sole proprietor, partner, or S-corp shareholder, the IRS gives two ways to avoid the underpayment charge entirely, and you only need to hit one of them, not both.

Option one: pay 90% of this year's actual tax. You estimate your current-year tax liability and pay at least 90% of it across the year through withholding and estimated payments combined. This requires a reasonably accurate forecast of the year you are still living through, which is the harder option if income is unpredictable.

Option two: pay 100% of last year's tax (110% for higher earners). You look at the total tax shown on last year's return and pay at least that much this year. If your adjusted gross income last year was over $150,000 (or $75,000 if married filing separately), the safe harbor rises to 110% of last year's tax instead of 100%.

The second option is usually easier to plan around because last year's number is already known and fixed, while this year's is a moving target. A business owner having a much better year than last year can safely underpay relative to their actual current liability and still owe zero penalty, as long as they meet the prior-year percentage. The trade-off is a larger balance due in April, just without the underpayment charge attached to it.

For a calendar-year individual, the four 2026 due dates are April 15, June 15, and September 15, 2026, then January 15, 2027 for the fourth. Notice the gaps are not even three-month quarters: there are two months between the first and second payments, three months between the second and third, and four months between the third and fourth. This is a quirk of how the rule was written decades ago and it has not changed.

Each payment is generally meant to cover a quarter of the year's expected liability, but because the calendar gaps are uneven, it is easy to assume you have more runway between payments than you actually do. Build the four dates into a recurring reminder rather than counting months from the last payment.

If a due date falls on a weekend or federal holiday, it moves to the next business day. Confirm the exact date for a given year, including any shift, against the current IRS Form 1040-ES instructions or Publication 505 before relying on a date printed anywhere else, including this guide.

Start with expected total income for the year: business profit, wages, investment income, anything taxable. Subtract expected deductions to land on estimated taxable income, then apply the tax brackets to get an estimated income tax figure. For anyone with self-employment income, whether a sole proprietor or a partner active in the business, add self-employment tax, which covers the Social Security and Medicare contributions an employee would otherwise split with an employer. This second piece is easy to forget and is often larger than people expect on a profitable small business.

Subtract any tax credits you expect to claim and any withholding already happening elsewhere, for example from a spouse's W-2 job or a part-time position. What is left is the amount still owed for the year. Divide that by four for the simplest version of quarterly payments, though a business with income that is heavily weighted toward one part of the year can use the annualized income installment method instead, covered further down.

Form 1040-ES includes a worksheet built for exactly this calculation, and most accounting or tax software will run the same math automatically once your projected numbers are entered. The output that matters is a specific dollar figure for the current quarter, not a rough sense of what the year might owe.

A C-corporation is a separate taxpayer from its owners, so it pays its own estimated tax on its own income, calculated on the corporation's tax return, generally Form 1120. For a calendar-year corporation, the four installments are due April 15, June 15, September 15, and December 15, each equal to 25% of the required annual payment, a cleaner split than the individual schedule.

The safe harbor works similarly to the individual rule at first glance: pay the lesser of 100% of the current year's tax or 100% of last year's tax. There is no 110% step-up for corporations the way there is for higher-earning individuals.

The trap sits in the definition of a large corporation: one with taxable income of $1 million or more in any of the three immediately preceding tax years. A large corporation can only use the prior-year safe harbor for its first quarterly installment. Every installment after that must be based on the current year's actual tax, with a true-up if the first installment was calculated on the prior-year method. A fast-growing business that crosses the $1 million mark can find itself required to switch methods mid-year without realizing the rule changed underneath it.

An S-corporation or a partnership is a pass-through entity for federal purposes: the entity itself generally does not pay federal income tax or federal estimated tax. Instead, profit flows through to the owners on a Schedule K-1, and each owner reports their share on their own personal return and pays personal estimated tax on it, following the individual rules above.

This means a profitable S-corp with three shareholders does not send the IRS a single corporate estimated payment. Each of the three shareholders separately estimates their own share of the profit, adds it to whatever else is on their personal return, and makes their own quarterly payments.

A growing number of states have added a separate pass-through entity (PTE) tax election, letting the entity itself pay state tax on behalf of its owners, usually to work around the federal cap on the state and local tax deduction. Where a state PTE election applies, the entity may owe its own state-level estimated payments in addition to what the owners pay personally. Check the specific state's rule if a PTE election is in place, since the mechanics and deadlines vary by state and this guide does not cover state PTE schedules.

It helps to stop thinking of this as a flat penalty and start thinking of it as interest on money the IRS believes should have been in its hands earlier. Individuals calculate it on Form 2210, corporations on Form 2220, and both forms work the same way conceptually: they look at each installment period separately, compare what was actually paid to what should have been paid under whichever safe harbor method you are using, and charge a rate on the shortfall for the number of days it was outstanding.

The rate itself is not fixed in the tax code as a flat percentage. It is tied to the federal short-term interest rate plus a few percentage points, and the IRS resets it every calendar quarter. Because it changes quarter to quarter, do not rely on a number quoted anywhere, including here. Check the current rate directly at the IRS's quarterly interest rate page before estimating what an underpayment would actually cost in dollars.

One detail that surprises people: even if you pay the full amount owed by April 15 and owe nothing further with your return, you can still owe an underpayment charge for an earlier quarter if that specific quarter's payment was too small at the time, calculated only up to the point a later payment caught it up. Catching up in Q4 does not erase a Q1 shortfall.

The simple approach, divide the year's expected tax by four, assumes income arrives evenly across the year. A landscaping business, a retailer with a holiday spike, or a consultant who closes one large contract in the fourth quarter does not earn that way, and paying a flat 25% in the first quarter of a business that has not made much money yet can create a real cash squeeze for no reason.

The annualized income installment method, using Schedule AI on Form 2210 for individuals or the equivalent worksheet on Form 2220 for corporations, lets you calculate each installment based on income actually earned up to that point in the year, annualized, rather than a flat quarter of the full-year estimate. A business that earns 70% of its annual profit in the last four months can show that the first two installments were properly smaller, because the income to support a larger payment had not happened yet.

This method takes more bookkeeping discipline: it only works if your books are current enough at each due date to know what has actually been earned so far, not a rough guess. A business with genuinely seasonal income and clean, current books usually benefits from this method. A business that just has irregular invoicing but roughly even underlying profit usually does not need it and adds paperwork for little payoff.

Consider a consulting S-corp with one owner. Last year the business generated $120,000 in taxable profit flowing through to the owner's personal return, and the owner's total tax on last year's return was $28,000. This year, the owner expects profit to grow to $180,000, largely because two new contracts landed in July and August, with an estimated current-year tax of roughly $42,000.

Using the prior-year safe harbor, since last year's AGI was under $150,000, the owner only needs to pay 100% of last year's $28,000 figure this year, split into four payments of $7,000 each on the individual due dates: April 15, June 15, and September 15, 2026, and January 15, 2027. That satisfies the safe harbor even though the owner will owe roughly $14,000 more with the April 2027 return once the year's actual, higher liability is finalized.

If the owner instead tried to pay only 90% of what they guessed the current year's tax would be, and guessed low before the two new contracts landed, say estimating $30,000 in tax and paying $6,750 a quarter, they would fall short of both the 90%-of-current-year test and the 100%-of-prior-year test once the real $42,000 figure is known, and would owe an underpayment charge on the shortfall for whichever quarters were short. The prior-year safe harbor was the safer bet here specifically because the business had a known, moderate prior year to lock onto.

The most common mistake is not paying at all until the return is filed in April, treating estimated tax as optional because nothing forces the payment before then the way payroll withholding forces an employer's hand. Nothing stops you from doing this, but the underpayment charge accrues quietly in the background the whole time, and it surprises people who assumed paying the full balance by the filing deadline was good enough.

A second common mistake is applying the individual safe harbor logic to a C-corporation, or assuming an S-corp itself owes federal estimated tax the way its shareholders do personally. The entity-level and personal rules are genuinely different regimes, and mixing them up produces either an unnecessary corporate payment or a missed personal one.

A third: forgetting self-employment tax in the estimate, which on a profitable sole proprietorship or active partnership can be a larger dollar figure than the income tax itself. And a fourth: a fast-growing business that crosses the large-corporation $1 million threshold without adjusting its estimated tax method for the installments after the first.

Our team builds the quarterly estimate from books we already keep current, tracks which safe harbor method applies to each entity and owner, and flags a required method change, like the large-corporation rule or a mid-year income jump, before a due date passes rather than after. The actual filing and payment still goes through a credentialed signer or your registered filing partner; we handle the calculation and the paperwork behind it.