The U.S. Tax Court is where you dispute a proposed deficiency without paying it first. It is a tool. Use it when it is the right one.
The 90-day deadline
Under IRC 6213(a), you have 90 days after the notice of deficiency is mailed (150 days if it is addressed to a person outside the United States) to petition the Tax Court. Miss it and you lose that forum.
Small tax cases
IRC 7463 allows simplified procedures when the amount in dispute for a year does not exceed $50,000. A decision in a small tax case cannot be reviewed by any other court and is not precedent.
Fraud penalties in Tax Court
When the IRS asserts fraud, IRC 7454(a) puts the burden of proof on the government. See civil vs. criminal tax fraud.
General information only, not legal advice. Reading this page does not create an attorney-client relationship. Laws and IRS procedures change; the sources cited were reviewed on the date shown above.