Quarterly Estimated Tax Calculator

Use this Weidner CPA decision tool to estimate federal tax payments from your prior-year return, expected current-year tax, withholding and payments already made. Gather your filing status, prior-year total tax and adjusted gross income, and current-year projections before you begin.

Example and assumptions

If prior-year total tax was $20,000 and expected current-year withholding is $8,000, a 100% prior-year target leaves $12,000, or $3,000 per installment under an equal-payment approach. This example assumes a full 12-month prior-year return, no higher-income adjustment, no payments already made and timely installments. A lower current-year target or special rules may change the result.

What the result means

A safe-harbor payment target can help manage underpayment penalties; it is not your final tax bill. Higher-income taxpayers may need a 110% prior-year target. Uneven income, missed installments, changing withholding, farming or fishing income and other exceptions require separate review. The tool does not calculate every penalty or replace a completed tax return.

Turn the estimate into a plan

Weidner CPA connects current bookkeeping with estimated-tax planning for San Antonio and Texas businesses. Explore year-round tax planning, CPA-led bookkeeping and pricing and plans.

Does the safe-harbor target equal my final tax bill?

No. It is a payment target for managing underpayment penalties. Your completed return may show additional tax due or a refund.

What if my business income changes during the year?

Update the projection as income, deductions or withholding change. Uneven income may require an annualized installment calculation rather than four equal payments.

Can I wait until tax filing to pay the full amount?

Waiting may leave an underpayment for an earlier installment period even if the final balance is paid at filing. Review payment timing as well as the annual total with your CPA.

Publisher and sources

Published by Weidner CPA. Firm principal: Edward Weidner, CPA. Educational estimates only. Official guidance: IRS estimated taxes and Publication 505.