Quarterly estimated tax calculator
If you're self-employed or have income with no withholding, paying too little during the year brings an underpayment penalty even if you pay in full in April. Use this to find federal and Alabama payments that keep you inside the safe harbor rules.
How much is enough
You avoid an underpayment penalty if withholding and estimated payments together reach the smaller of two amounts: 90% of this year's tax, or 100% of last year's. If last year's adjusted gross income was over $150,000, or $75,000 married filing separately, the prior-year figure rises to 110%. Alabama uses the same structure, with a $500 threshold where the federal rule uses $1,000.
The prior-year route is the one most people should use, because it is a number you already know. Paying 90% of this year's tax only helps when you are confident this year will come in lower.
When it is due
For 2026: April 15, June 15 and September 15, 2026, then January 15, 2027. For 2027: April 15, June 15 and September 15, 2027, then January 18, 2028, because January 15 falls on a Saturday and the Monday after is Martin Luther King Jr. Day. Alabama's dates match.
Common questions
My income is uneven. Do I have to pay equal amounts?
No. The annualized installment method on Form 2210 lets you match payments to when the income arrived, which can lower the early installments. It takes more work at return time.
I own an S corporation. Can I withhold more instead?
Often, yes. Withholding is treated as paid evenly across the year, whenever it actually came out of your pay, which makes extra withholding through your own payroll a useful way to catch up late in the year.
Estimated payments are part of our tax services, and the deadline calendar lists these dates alongside everything else a business files.
More free tools: the Alabama business tax deadlines calendar, the S corporation tax savings calculator, and all our calculators.
Important: This calculator gives a general estimate for planning only. It is not tax, legal or financial advice, and using it does not make you a client of Titus CPAs. Results rely on the numbers you enter and on simplified assumptions. Tax rules, rates and deadlines change, so the results may be incomplete or wrong for your situation. Figures last reviewed October 2026. Before you file, pay or make a decision, confirm the result with your tax professional. If you don't have one, you can contact us.
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