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California · paying as you go
California asks for 30, 40, 0 and 30. In that order.
The federal installments are four roughly equal payments. California’s are not equal, are not in the order you would guess, and the September one is nothing at all. Budgeting them as quarters is how a practice ends up short in June.
In short
How much do I send each quarter?
Two schedules, the front-loaded California shape, and the safe harbour
30/40/0/30 California installmentsTwo schedules, not one
A private practice has no employer withholding anything, so the tax arrives in installments you send yourself. There are two sets of them, they share three of their four dates, and they divide the year completely differently.
The federal installments are what you would expect — four payments, one per quarter, 15 April, 15 June, 15 September and 15 January.[2]
California’s are not:
| Installment | Due | Share of the year |
|---|---|---|
| First | 15 April 2026 | 30% |
| Second | 15 June 2026 | 40% |
| Third | 15 September 2026 | 0% |
| Fourth | 15 January 2027 | 30% |
That third line is not a typo and it is the thing worth knowing. California asks for nothing in September. It has already asked for 70% of the year by 15 June.[1]
Why the shape matters more than the dates
A therapist who budgets “a quarter each quarter” is fine federally and 40% short in June. The California year is front-loaded: seventy per cent of it lands in the first two months of the tax calendar, before most practices have had a chance to earn it.
In a growing practice this is uncomfortable but survivable. In a practice with a seasonal shape — and therapy has one, with the summer dip most private practices know — a 40% payment due on 15 June, computed on last year, arrives at close to the worst possible moment.
The September zero is not a gift. It is the reason June is 40%.
The safe harbour, which is the part that actually protects you
You are not required to guess this year correctly. Both systems let you pay by reference to last year instead, and a year you have already filed is a number rather than a forecast.
- Federal. Pay the lesser of 90% of the current year’s tax, or 100% of last year’s. If last year’s adjusted gross income was above $150,000 ($75,000 married filing separately), the prior-year figure rises to 110%.[2]
- California. The same structure and the same threshold: 100% of last year, or 110% if last year’s California AGI was above $150,000 ($75,000 married filing separately).[1]
- And one more California rule that will not apply to most readers but is absolute when it does: at a current-year California AGI of $1,000,000 or more, the prior-year safe harbour disappears entirely and you must pay on 90% of the current year.[1]
The practical consequence is worth stating plainly. In a year your income is rising, paying on last year is the cheaper arrangement — you keep the difference until April and owe no penalty. In a year your income is falling, paying on last year means lending the state money you did not have to.
What this does not decide
Nothing on this page tells you the amount. It tells you the fractions and the dates the fractions attach to, which is only useful once you have a year’s tax to divide.
And a caution about the safe harbour specifically: it protects you from the penalty, not from the bill. Paying 100% of a small prior year through a large current one is entirely legal and leaves the whole difference due in April. That is a cash-flow decision rather than a tax one, and it is the one people regret.
Every installment on this page is a share of one annual figure, so the installment is only as good as that figure. The tax page computes the year — federal, California, self-employment — on your own profit.
Open the calculator →Sources
- Franchise Tax Board — Estimated tax payments — the 30/40/0/30 installment percentages and their due dates; the 100% and 110% prior-year safe harbours and the $150,000 threshold; the 90% current-year requirement above $1,000,000 of California AGI
- IRS — Estimated tax, frequently asked questions — the four federal payment periods and due dates; 90% of the current year or 100% of the prior year, rising to 110% above $150,000 of prior-year AGI
Every figure here is either computed by the calculator linked above from numbers you enter, or quoted from the source named beside it. Nothing on this page is illustrative. This is not legal, tax or financial advice, and reading it does not create a professional relationship.