RSU Safe Harbor Checker
Avoid the IRS underpayment penalty. 100% private, client-side calculation.
Why is this safer than other apps?
Other Apps: "Encryption"
Competitors often encrypt your data but still upload it to their database. This means your salary info lives on a server you don't control. If their keys are lost or the server is hacked, your data is at risk.
This App: "Zero-Upload"
We don't need encryption because we don't touch your data. The math happens entirely in your browser (Client-Side). You can literally turn off your WiFi before using this tool, and it still works perfectly.
How to Avoid the IRS Underpayment Penalty on RSUs
If you receive Restricted Stock Units (RSUs) as part of your compensation, you are likely at risk of the IRS Underpayment Penalty. This happens because most employers only withhold a flat 22% for taxes, even if you are in the 32%, 35%, or 37% tax bracket.
What is the IRS Safe Harbor Rule (2025)?
The IRS offers a "Safe Harbor" rule to avoid penalties. You will not be penalized if you pay at least:
- 90% of the tax you owe for the current year, OR
- 100% of the tax you paid last year (110% if your AGI is over $150k).
This RSU Safe Harbor Calculator helps you check if you meet the 110% rule instantly. It runs 100% offline in your browser, ensuring your financial data remains private.
Do I need to pay quarterly taxes?
If our calculator shows you are "At Risk," you should consider making an estimated tax payment (Form 1040-ES) by the quarterly deadline (April 15, June 15, Sept 15, Jan 15) to close the gap.
*Disclaimer: Not financial advice. Calculations based on IRS 2024/2025 Safe Harbor rules (110% of prior year tax).