An educational estimate — not advice.

Not professional advice

The information and estimates on this site are provided for general educational purposes only. They are not tax, legal, financial, or accounting advice, are not a substitute for advice from a qualified professional, and don't create any advisory relationship. Estimated-tax decisions have real financial consequences — before you act, confirm your situation with a CPA, an enrolled agent, or the IRS.

Estimates, not determinations

The calculator produces an estimate, not a determination of what you owe or a guarantee against a penalty. In particular:

• Safe harbor. The tool computes the lower of 90% of the current year's projected tax or 100%/110% of the prior year's tax, per IRS Publication 505. Your actual liability depends on your final return.
• Self-employment tax. The Social Security portion applies only up to the annual wage base announced by the SSA, and the calculator uses the figure current when the tax year's data was last refreshed. Verify the wage base for your year.
• State schedules. State estimates use each state's published brackets and the standard deduction; states with their own add-backs, exemptions, or credits will differ. Confirm against your state's own estimated-tax form.
• Underpayment interest. Any penalty figure uses the Section 6621 rate shown, which the IRS changes every quarter. Check the current published rate before relying on it.

Time-sensitive and subject to change

Tax figures change on a schedule: the Section 6621 interest rate quarterly, the Social Security wage base annually, and the federal brackets and standard deduction annually. The four federal due dates (April 15, June 15, September 15, and January 15) shift to the next business day on weekends and holidays. This tool models current published rules; verify dollar thresholds, rates, and dates against primary sources before relying on them.

Out of scope

This tool covers individuals and pass-through owners paying estimated tax for their state of residence. It does not handle multi-state apportionment, city or local business taxes, corporate (Form 1120) estimates, quarterly sales tax, or the precise per-quarter penalty computation. For those, and for genuinely lumpy income handled under the annualized installment method on Form 2210 Schedule AI, consult a tax professional.

Verify before you rely on it

To pay, use IRS Direct Pay or EFTPS, and consult IRS Publication 505 and your state's department of revenue. We do our best to keep figures accurate and to cite primary sources, but we make no warranty of accuracy or completeness and accept no liability for decisions made based on this site. See our terms of use.

No affiliation

quarterlytaxplan.com is an independent tool operated by Red Goggles LLC. It is not affiliated with, endorsed by, or connected to the IRS, any state tax agency, or any tax-preparation or tax-software company.

Last updated: May 31, 2026