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Quarterly estimates: the safe harbor that ends penalty anxiety
The short answer
Nothing is withheld from self-employment income, so the IRS expects quarterly payments — and penalizes underpayment. The escape is the safe harbor: pay 100% of last year's tax (110% if AGI was over $150k) in four installments and penalties vanish no matter how good this year gets. Our calculator computes the payments in ten seconds; the planning is in the exceptions — lumpy income and state rules like California's front-loaded 30/40/0/30 schedule.
How it works
- Pull last year's total tax from the 1040; apply 100% or 110%.
- Divide by four; pay by the four due dates (mind the short Q2).
- Reduce for withholding you or a spouse will have — withholding counts as paid evenly all year, a powerful year-end fix.
- Lumpy income? Annualize instead of guessing.
- Run the state separately — California's schedule and thresholds are their own animal.
Frequently asked questions
What are the safe-harbor rules?
Pay 100% of last year's total tax (110% if prior-year AGI exceeded $150,000) in equal quarterly installments and federal underpayment penalties disappear regardless of what you owe in April.
When are the payments due?
April 15, June 15, September 15, and January 15 — note the uneven spacing; Q2 covers only two months.
What if my income arrives unevenly?
The annualized income method matches payments to when income actually arrived — more math, fairer result for lumpy earners; Form 2210 Schedule AI does the reconciliation.
Do states have their own rules?
Yes, and they differ — California front-loads payments (30/40/0/30) with its own thresholds. Federal safe harbor does not protect you from state penalties.
Want quarterlies off your mind?
Monthly-service clients get payments computed, scheduled, and reminded automatically — federal and state.
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