Quarterly Estimated Tax Calculator (US)

Quarterly Estimated Tax Guide

What should I know about Who Needs to Pay Quarterly Tax?

Anyone whose tax withholding doesn't cover their total tax liability needs to make quarterly estimated payments to avoid the IRS underpayment penalty. Common situations: (1) Self-employed / 1099 contractors — no withholding by default. (2) S Corp owners — withholding on salary may not cover total tax. (3) Rental property income. (4) Investment income (significant interest, dividends, capital gains). (5) Side businesses while W-2 employed. (6) Retirees living off IRA withdrawals without withholding enough tax, since IRA withdrawals don't automatically have tax withheld the way a paycheck does.

What do I need to know about Safe Harbor Rules — Penalty Avoidance?

The IRS won't penalize underpayment if you meet ONE of these safe harbors: (1) Owe less than $1,000 at filing. (2) Paid at least 90% of CURRENT year tax through withholding + estimates. (3) Paid 100% of PRIOR year tax (110% if prior year AGI exceeded $150k, $75k MFS). The prior-year safe harbor is the safest: it's a KNOWN number. Strategy: divide prior year tax by 4, pay that each quarter. Won't avoid the actual tax owed — but eliminates penalty. Particularly valuable in spike-income years — a large one-off business sale or bonus, for example — since safe harbor lets you base payments on last year's more typical income instead.

What should I know about Payment Schedule and Methods?

Quarterly payment due dates (federal): Q1 — April 15 (for Jan-Mar income). Q2 — June 15 (Apr-May). Q3 — Sept 15 (June-Aug). Q4 — January 15 of following year (Sept-Dec). Q4 is the LAST chance to avoid prior-year penalty. Payment methods: IRS Direct Pay (free, from bank account, irs.gov/payments). EFTPS (Electronic Federal Tax Payment System — required for large businesses, simpler for individuals once set up). Credit card via authorized processors (1.85-1.99% fee — usually NOT worth it unless you're specifically chasing credit card rewards points that outweigh the processing fee.

What should I know about Self-Employment Tax Calculation?

SE tax is the self-employed version of Social Security + Medicare. Calculation: SE income × 92.35% × 15.3% (under SS wage base $176,100), then × 2.9% for income over wage base, then additional 0.9% Medicare for SE+wages over $200,000 single / $250,000 MFJ. Half of SE tax is deductible as adjustment to gross income (line 15 of Schedule 1) — reduces income tax but not SE tax itself. Worked example: $60,000 self-employment income. Net earnings $55,410 (92.35% × $60k). SS portion: $55,410 × 12.4% = $6,871. Medicare portion: $55,410 × 2.9% = $1,607. Total self-employment tax: approximately $8,478 before any income tax is even calculated.