As long as you do not consent to assessment of income taxes and you respond timely to any Statutory Notice of Deficiency, you may contest the proposed assessment without having to first pay the tax. A Statutory Notice of Deficiency most normally provides a 90 day window in which you may petition the United States Tax Court. The time limit is strictly enforced and it is jurisdictional. A petition filed [mailed] on the 91st day is too late. Normally, trials in the United States Tax Court occur from 1 to 1 and ½ years after the petition filing date. Only a lawyer admitted to practice before the United States Tax Court may file a petition for you.
For taxes other than Income Taxes and for taxes already assessed, you must either pay the tax first and then file a claim for refund or file a bankruptcy petition and have the United States Bankruptcy Court determine the tax liability. Only a lawyer admitted to practice before the United States District Court for the judicial district1where you have resided2, may represent you in Bankruptcy Court.
1» There are two federal judicial districts in the State of Washington, Western and Eastern.