Quarterly estimated taxes: a founder's simple guide
Learn who must pay quarterly estimated taxes, the 2026 due dates, how to calculate payments, and how to avoid IRS underpayment penalties as a founder.
By Initio Editorial Team · · 4 min read
The short answer
Founders who expect to owe $1,000+ in federal tax (or take owner draws/distributions without withholding) must pay quarterly estimated taxes using Form 1040-ES, due April 15, June 15, September 15, and January 15. Pay at least 90% of this year's tax or 100-110% of last year's to avoid penalties.
Key takeaways
- Quarterly estimated tax deadlines for 2026 are April 15, June 15, September 15, and January 15, 2027.
- You generally must pay if you'll owe $1,000 or more in federal tax and don't have enough withheld.
- Use the 'safe harbor' rule — pay 100% (110% if prior-year AGI exceeded $150,000) of last year's tax liability — to avoid underpayment penalties regardless of this year's income.
- S-corp owners on payroll can often cover taxes via withholding instead of quarterly vouchers, simplifying cash flow.
- Set aside 25-35% of net owner income in a separate account to avoid a cash crunch each quarter.
Who has to pay quarterly estimated taxes?
If you're a founder who takes owner draws, earns self-employment income, or receives distributions from an LLC or S-corp without enough tax withheld, the IRS expects you to prepay your tax bill in installments rather than waiting until April 15. The general rule: you must make estimated payments if you expect to owe $1,000 or more in federal tax for the year after subtracting withholding and credits.
This applies to most solo founders and partners in an LLC vs C-corp structure that passes income through to your personal return. C-corp founders who pay themselves a W-2 salary typically have taxes withheld automatically and may not need to file 1040-ES vouchers — but the corporation itself may owe estimated corporate tax if profitable.
Self-employment tax adds up fast
Beyond income tax, self-employed founders and LLC members owe self-employment tax of 15.3% (12.4% Social Security up to the wage base, plus 2.9% Medicare, with no cap) on net earnings. For 2025, the Social Security wage base is $176,100; the 2026 figure will be released by the Social Security Administration in fall 2025, typically rising a few percent. This is on top of ordinary federal and state income tax, which is why many founders are shocked by their first estimated tax bill.
2026 quarterly due dates
| Payment period | Due date |
|---|---|
| Q1: Jan 1 - Mar 31 | April 15, 2026 |
| Q2: Apr 1 - May 31 | June 15, 2026 |
| Q3: Jun 1 - Aug 31 | September 15, 2026 |
| Q4: Sep 1 - Dec 31 | January 15, 2027 |
Note the periods are uneven — Q2 is only two months and Q3 is three. If a due date falls on a weekend or federal holiday, it shifts to the next business day. These are separate from payroll tax deadlines like Form 941 quarterly filings, which follow their own calendar.
How to calculate your estimated payment
The IRS provides Form 1040-ES with a worksheet, but the simplest approach for most founders is:
- Estimate your total expected taxable income for the year, including salary, distributions, and any 1099 income.
- Calculate expected federal income tax using current brackets, plus self-employment tax if applicable.
- Subtract any withholding already happening (e.g., from a W-2 salary).
- Divide the remaining balance by four to get your quarterly payment, or front-load based on when income actually arrives.
The safe harbor shortcut
Most founders don't know their exact annual income in January. The IRS safe harbor rule lets you avoid penalties entirely by paying either:
- 90% of your current year's actual tax liability, or
- 100% of last year's total tax liability (110% if your prior-year adjusted gross income was over $150,000, or $75,000 if married filing separately).
Paying based on last year's return is far easier to calculate and still protects you from the underpayment penalty, even if this year turns out to be much more profitable.
How to pay
- Calculate your quarterly amount using Form 1040-ES or your prior-year safe harbor figure.
- Pay online via IRS Direct Pay or EFTPS (Electronic Federal Tax Payment System) — both are free and let you schedule payments in advance.
- Keep the confirmation number for your records in case of a filing dispute.
- Repeat each quarter, adjusting the amount if your income changes significantly.
- Reconcile on your annual return — any shortfall is due April 15, and overpayments are refunded or applied forward.
Most states with income tax (e.g., California, New York) require their own separate quarterly estimated payments, often on similar but not identical schedules — check your state department of revenue.
What happens if you miss a payment or underpay
The IRS charges an underpayment penalty calculated using the federal short-term interest rate plus 3 percentage points, applied quarterly on the shortfall. It's not catastrophic for a quarter or two, but it compounds and signals to the IRS that your estimates are off. If you miss a full quarter, pay as soon as possible — the penalty clock resets once you catch up, and paying late is always cheaper than not paying at all.
If your income is highly seasonal or unpredictable (common for founders with lumpy revenue), Schedule AI of Form 2210 lets you annualize income and reduce penalties tied to an uneven payment schedule.
Setting aside cash so quarterly taxes don't hurt
The most common founder mistake isn't miscalculating taxes — it's spending the cash before the deadline arrives. A simple system:
- Open a separate savings or tax-reserve account and automatically transfer 25-35% of every owner draw or distribution into it.
- Treat that money as already spent; don't dip into it for operating expenses.
- Reconcile quarterly against your actual 1040-ES calculation and adjust the percentage up or down.
Some business banking platforms, including Initio Treasury, support sub-accounts or "envelopes" that make it easier to automatically set aside a percentage of incoming revenue for taxes without manual transfers.
Quarterly taxes vs. payroll withholding
If you run payroll for yourself as an S-corp or C-corp employee, you can increase your W-2 withholding instead of sending quarterly vouchers — withholding is treated by the IRS as paid evenly throughout the year regardless of when it's actually withheld, which can retroactively cure an underpayment from earlier quarters. This is a useful lever late in the year if you've fallen behind on estimates.
Ultimately, quarterly estimated taxes are a cash-flow discipline problem as much as a tax calculation problem. Build the habit early, automate what you can, and loop in a CPA once your income crosses the point where manual estimates feel risky — particularly around fundraising events, equity sales, or your first profitable year. For broader compliance timing, see our startup compliance calendar.
Frequently asked questions
Do I need to pay quarterly estimated taxes if I'm pre-revenue?
If you have no taxable income or your withholding already covers your liability, you generally don't need to make estimated payments. Once you start taking draws or distributions, reassess each quarter.
What is the penalty for not paying quarterly estimated taxes?
The IRS charges interest-based underpayment penalties calculated at the federal short-term rate plus 3%, applied to the shortfall for each quarter it remained unpaid, until you catch up or file your annual return.
Can I pay all my estimated taxes at once instead of quarterly?
You can prepay the full year's estimate in Q1, which eliminates future estimated tax penalties, but it ties up cash earlier than necessary. Most founders prefer spreading payments to match cash flow.
Do S-corp owners pay quarterly estimated taxes?
S-corp owners who take a reasonable W-2 salary usually have income tax withheld through payroll, which can reduce or eliminate the need for separate 1040-ES payments, though distributions above salary may still require estimates.
What tax form do I use to pay quarterly estimated taxes?
Individuals use Form 1040-ES to calculate and submit payments, typically paid online through IRS Direct Pay or EFTPS. C-corporations use Form 1120-W for corporate estimated tax.
