If you've received a Notice of Deficiency from the IRS, the short answer to the question is hire a tax attorney immediately. A Notice of Deficiency results after the IRS has examined (audited) your return and determined you owe additional taxes. The Notice of Deficiency allows you to go to the Tax Court and tells you the procedure to follow. You have a limited amount of time to respond before forfeiting your rights. If you don't respond within the prescribed time, the IRS will send you a bill for the additional tax due. You have 90 days from the date this notice is mailed to you to file a petition with the Tax Court (or 150 days if the notice is addressed to you outside the United States). The last date to file your petition will be entered on the notice of deficiency issued to you by the IRS. If you discuss your case with the IRS during the 90-day period (150-day period), the discussion will not extend the period in which you may file a petition with the Tax Court. The court will schedule your case for trial at a location convenient to you. You may represent yourself before the Tax Court, or you may be represented by anyone permitted to practice before that court.