What it is
Clients with self-employment, investment or other income not covered by withholding need quarterly estimates. The calculator projects the year, applies the bracket table you enter, adds self-employment tax and other taxes and finds the required annual payment under the safe harbor you choose.
It splits what remains into four installments with due dates adjusted for weekends and checks cumulative payments against cumulative required amounts. The safe harbor percentages and the self-employment rates are pre-filled from the statute. You enter the tax year, the bracket table and the Social Security wage base.
When to use it
- Setting quarterly estimates for clients.
- Mid-year reprojection after a change in income.
- Explaining safe harbor options to a client.
What’s inside
- Brackets tab for the ordinary rate table
- Income to taxable income and total tax
- Safe harbor comparison and required payment
- Four installments with due dates and a funded or short status
Standard cited
This template follows IRC 6654 / Form 1040-ES. It is written in our own words, except for phrases the standard requires the document to contain, with [bracketed placeholders] for client details, amounts in USD and dates as MM/DD/YYYY. Check it against the current standard and your firm’s methodology before use.
Questions
What are the safe harbors?
Under IRC 6654 the required annual payment is generally the smaller of 90% of current-year tax and 100% of prior-year tax, with 110% of prior-year tax when prior-year AGI is above $150,000 ($75,000 if married filing separately). The calculator uses those figures.
Does it compute the penalty?
No. It checks installments against required amounts. The penalty is figured on Form 2210.
Does it handle AMT?
Enter AMT, net investment income tax and additional Medicare tax in the other taxes line.
Related templates
- Individual Tax Return Review Checklist
- Tax Extension and Due Date Tracker (Excel)
- Income Tax Provision Workbook (ASC 740)
- Tax Return Preparation Engagement Letter
Last updated 11/05/2026. All free templates.