When dealing with the 90-day deadline for filing a Tax Court petition, you must ensure the IRS has your most up-to-date address. The 90-day period starts from the date listed on the IRS Notice of Deficiency, not when it is received. If you are outside the U.S. when the Notice of Deficiency is mailed to you, you have 150 days to file a Tax Court petition. This deadline is strict – if missed, your case will be dismissed. To avoid this, act quickly. Missing the deadline may leave you with the option of paying the tax in full and suing for a refund in another federal court. If the IRS sends this notice to an outdated address, you risk missing the deadline, which can result in your case being dismissed. Filing Form 8822 (Change of Address) ensures you receive critical IRS correspondence promptly. For more information, you can visit the IRS website.