Why are 90 day letters from the IRS known as "your ticket to Tax Court?" Statutory Notices of Deficiency, otherwise known as 90 day letters are known as your ticket to Tax Court, because the only way you can get into the US Tax Court is after you have received one. Why is this important? It is important because this is the only court where you can argue your tax position without first having paid the tax. In other courts you must first pay the tax, and then sue for a refund of your money. Not so with the U.S. Tax Court.
Why is it important that these are called 90 day letters? It is very significant that the Statutory Notice of Deficiency is called a 90 day letter, because when you receive the letter you have exactly 90 days from the date of the letter to file a petition in the United States Tax Court. There are absolutely no extensions of time beyond this 90 day period. The IRS must send you this letter by Certified Mail. The letter indicates that you have 90 days to file the petition of pay the tax. If you do not file the petition, you are foreclosed from arguing your case before the US Tax Court. This does not mean that you cannot take your case to the US District Court or the Court of Claims. It just means that you will have to pay the tax first.
In certain situations it may actually be better to go to a court other than the US Tax Court. This is a decision best made with your attorney in the matter. Just make sure you consider this decision prior to the end of the 90 day period so that you still have the option available.