The Petitioner Decides the Issues
You are the plaintiff in a Tax Court case so you choose the issues. That is to say, you are suing the IRS. Although we have become accustomed to the idea that American citizens are “innocent until proven guilty” that’s not how it works in Tax Court. The IRS is the defendant, or respondent. You are the plaintiff, called the petitioner. You have the burden of proof to show you do not owe the money the IRS claims you owe. See Tax Court Rule 142(a).1
The Petition is Where You Identify the Issues
Proving you don’t owe something is a daunting burden. As the petitioner, however, you determine what the trial will be about. You say what the trial will be about in your Petition. You do it in two sections, Errors and Facts. Your Petition tells the court what you believe the IRS did incorrectly, and you state the facts on which you base your error claims. The trial will be held to settle the facts related to the issues/errors you raise in your petition.
You will be able to object to any attempt by your opponent to bring up issues that are “outside the pleadings” and he will have the burden of proof on any increases in the deficiency or “new matters” that he wants the Court to consider. New matters are issues that did not appear in the notice that got you to Tax Court. Check the Answer you receive to your petition carefully to see if any new issue appears there in the form of an allegation not made in the notice. If you find one, the respondent will have the burden of proof on it. Otherwise, you state the issues in your petition, and it is up to you to keep the trial focused on those issues.