Quarterly Tax Set-Aside

That 92.35% multiplier is a direct IRS rule — Schedule SE (Form 1040), Part I, Line 4a instructs filers to "multiply line 3 by 92.35% (0.9235)" — meant to roughly approximate the fact that a traditional employee's wages for payroll tax purposes are already net of the employer's matching share. Applying it to your net self-employment income before calculating the 15.3% self-employment tax rate keeps the estimate aligned with how the IRS actually computes it on Schedule SE.

The IRS lets you deduct half of your self-employment tax from taxable income for federal income tax purposes, so this calculator estimates SE tax first, subtracts half of that from taxable income, and only then applies your effective federal rate to the reduced figure. State tax in this calculator is applied to the un-reduced taxable income instead, since not all states honor that federal deduction.

It assumes a biweekly pay or invoicing rhythm — 26 periods in a year — rather than monthly, dividing total annual tax by 26 so you can set aside a consistent amount each time you get paid instead of trying to save a lump sum quarterly. If you invoice monthly instead, divide the Quarterly Payment figure by 3 for the equivalent monthly amount.

No — it applies your entered effective tax bracket as a single flat rate across your full taxable income rather than running income through the actual progressive bracket structure, and it doesn't subtract the standard deduction or any credits. It's designed to give a safe-to-set-aside estimate, not to replicate an actual tax return, so the real bill from a completed return will typically come in somewhat lower.