Blog · · 2 min read
Quarterly taxes without an accountant
Self-employed with no withholding? One monthly number, four uneven deadlines and the safe harbor rule, so the June payment stops being a surprise.
When you work for yourself, nobody withholds anything. Every client payment arrives whole, and some of it was never yours. The IRS expects that part in four installments a year, and the deadlines don't wait for a good month.
Here's the whole system in one page: one number to move every month, the four dates, and the rule that keeps you out of penalties.
The four dates aren't quarters
Estimated tax for a year is due on April 15, June 15, September 15 and January 15 of the following year, moved to the next business day when the date falls on a weekend or holiday. (IRS Form 1040-ES)
They're called quarterly payments, but the periods they cover aren't equal:
| Due | Covers income from | Months |
|---|---|---|
| April 15 | January–March | 3 |
| June 15 | April–May | 2 |
| September 15 | June–August | 3 |
| January 15 | September–December | 4 |
That's why June feels early and January feels heavy. If you set aside the same amount every month, January's payment is twice June's.
One number a month
The habit that works: every time a client pays you, move a fixed percentage to a separate savings account you don't spend from. Then each deadline is a transfer, not a scramble.
The percentage has three parts:
- Federal income tax at your bracket.
- Self-employment tax: 15.3% for Social Security and Medicare on most of your net earnings, dropping to 2.9% above the Social Security wage base ($184,500 in 2026).
- State income tax, if your state has one.
For a high-earning consultant, those add up to somewhere around 28% before state tax. In California that's roughly 37% of each payment; in Texas, 28%. It's a starting point, not a filing number: business expenses, retirement contributions and deductions all lower it.
See your monthly number and next four payments in the quarterly tax calculator.
The safe harbor
You don't have to predict this year's tax exactly. The IRS doesn't charge an underpayment penalty if you pay, on time, at least the smaller of:
- 90% of this year's tax, or
- 100% of last year's tax, or 110% if last year's adjusted gross income was over $150,000.
(IRS: underpayment of estimated tax)
In a year when your income is rising, the prior-year rule is often the easier target. Divide last year's total tax (times 110% if it applies) by four and pay that on each date. You'll owe the rest in April, but without a penalty, and the monthly set-aside means the money is already there.
When a month runs hot or cold
Self-employed income is lumpy, and the set-aside should follow it. A percentage of each payment does this on its own: a big month sets aside more, a thin month less. What it doesn't do is tell you whether the account will hold enough on the 15th.
That's the question Headroom answers. It puts your income on a 12-month projection with low, base and high cases, keeps the tax reserve apart from what you can spend, and flags a deadline before the reserve falls short. No bank login, ever.
This is general information, not tax advice. Your situation may differ; talk to a tax professional before acting on it.