TL;DR: If you're self-employed and expect to owe $1,000+ in tax, the IRS wants four payments a year — April 15, June 15, September 15, and January 15. Hit a safe harbor (100%/110% of last year's tax, or 90% of this year's) and you avoid penalties. Set aside ~25–30% of net profit as you earn it, and the whole thing stops being scary. The scramble only happens when you don't know your numbers — which is a bookkeeping problem, not a tax problem.
Nobody warns you about estimated taxes until your first one is late. When you had a job, your employer withheld taxes from every paycheck and quietly sent them to the IRS. Now you're the employer, the employee, and the payroll department — and the IRS still expects its money on a schedule.
The good news: it's mechanical once you understand the rules. The panic comes from not knowing your income, not from the tax itself.
Who actually has to pay
If you're in the US and you expect to owe about $1,000 or more in tax for the year after subtracting any withholding, you're on the hook for quarterly estimated payments. That sweeps in most founders:
- Freelancers and solo founders with no employer withholding at all.
- Single-member LLC owners — your business income flows to your personal return on Schedule C, and no one's withholding from it.
- Partners and multi-member LLC members taking guaranteed payments or profit shares.
- S-corp owners who take distributions on top of a salary — your payroll covers the salary, but distributions usually aren't withheld against.
If a real paycheck with real withholding covers most of your tax, you may be off the hook. For nearly everyone running their own thing, assume you're in.
The four dates (and why they're weird)
Mark these now. The IRS splits the year into four payment periods, and the due dates are not evenly spaced:
| Payment | Covers income from | Due |
|---|---|---|
| Q1 | Jan 1 – Mar 31 | April 15 |
| Q2 | Apr 1 – May 31 | June 15 |
| Q3 | Jun 1 – Aug 31 | September 15 |
| Q4 | Sep 1 – Dec 31 | January 15 (next year) |
Yes, the second "quarter" is two months and the fourth is four. Don't fight it — just put all four dates in your calendar with a reminder a week ahead. If a date lands on a weekend or holiday, it rolls to the next business day.
Safe harbor: the rule that kills the anxiety
Here's the part that lets you stop guessing. You don't have to predict your taxes perfectly. You just have to clear a safe harbor, and you avoid the underpayment penalty even if you end up owing more in April.
You're generally safe if your total payments for the year equal at least:
- 90% of what you owe this year, or
- 100% of what you owed last year — bumped to 110% if your prior-year adjusted gross income was over $150,000.
The second option is the easy button. Last year's tax is a known, fixed number sitting on your prior return. Divide it by four, pay that each quarter, and you've cleared the bar regardless of how this year shakes out. If you have a breakout year, you'll owe the difference at filing — but no penalty.
The 90%-of-this-year option is better when your income drops, because you don't want to overpay based on a bigger prior year. That's exactly where knowing your current numbers pays off.
How to estimate without a spreadsheet meltdown
For the rule-of-thumb crowd, here's the move that works for most founders:
- Track your net profit — revenue minus business expenses — as the year goes.
- Set aside 25–30% of it in a separate savings account the moment money comes in. Treat that account like it isn't yours, because it isn't.
- Pay your safe-harbor amount each quarter from that bucket.
- True up at year-end with your CPA.
Why 25–30%? Because as a self-employed person you're paying ordinary income tax plus self-employment tax (~15.3% covering Social Security and Medicare) on your net profit, often plus state tax. The exact rate depends on your bracket and state — but a 25–30% set-aside keeps you covered in most cases and is far better than the alternative of setting aside nothing.
The founders who get burned aren't the ones who estimated slightly wrong. They're the ones who spent the tax money because it was sitting in their checking account looking like revenue.
The real reason quarterly taxes feel like a fire drill
Notice what every step above depends on: knowing your net profit at any moment.
When your books are weeks or months behind, every quarterly deadline becomes a reconstruction project. You're digging through bank statements, guessing at categories, and trying to remember whether that $4,000 transfer was income or you moving your own money. You end up either overpaying out of fear or underpaying and eating a penalty.
When your books are current, the quarterly payment is a 10-minute task. You open your numbers, look at net profit for the period, apply your rate or your safe-harbor figure, and pay. No archaeology.
This is the whole argument for keeping books current instead of perfect: the payoff isn't tidy spreadsheets, it's that decisions like this stop being stressful. That's where Prosper fits — it auto-categorizes ~80–90% of your transactions from the merchant, amount, and your past choices, and surfaces only the handful of exceptions for you to review. Most founders clear that review in an afternoon, which means your net-profit number is always close at hand when a due date rolls around. Knowing what you've actually earned is the entire game with estimated taxes.
A no-panic checklist
- Confirm you're in scope. Expecting to owe $1,000+ with no withholding? You're paying quarterly.
- Calendar all four dates — Apr 15, Jun 15, Sep 15, Jan 15 — with a one-week heads-up.
- Pick your safe harbor. Last year's tax ÷ 4 is the simplest; use 90% of this year if your income dropped.
- Open a separate tax-savings account and route 25–30% of net profit into it as you earn.
- Pay via IRS Direct Pay or EFTPS — and don't forget your state, which usually has its own quarterly schedule.
- Keep your books current so every quarter is a lookup, not a reconstruction.
Estimated taxes feel scary because they arrive without a manager reminding you and without withholding doing the work. But the rules are fixed, the dates are known, and the only genuinely hard part — knowing your income — is solved by bookkeeping you should be doing anyway.
FAQ
Who has to pay quarterly estimated taxes?
In the US, anyone who expects to owe roughly $1,000 or more in tax and doesn't have enough withheld for them — that's most self-employed people, single-member LLC owners, partners, and S-corp owners taking distributions on top of salary. If you're a freelancer or founder with no employer withholding, assume it applies to you.
How much should I set aside for estimated taxes?
A common rule of thumb is 25–30% of your net profit (revenue minus expenses), set aside as you earn it. Your real rate depends on your bracket, state, and self-employment tax, so treat 25–30% as a safe default and refine with a CPA. The key is putting it aside in real time, not finding it at the deadline.
What is the safe-harbor rule for estimated taxes?
You can generally avoid an underpayment penalty by paying either 90% of this year's tax or 100% of last year's tax (110% if your prior-year income was over $150k) across your four payments. Paying last year's number is the simplest safe harbor because you already know it — and with current books, you always know this year's too.
Not professional tax or accounting advice. Consult a CPA for your situation.