If you disagree with the IRS’s findings after an audit, you have several options: 1) Request an appeal within the IRS by filing a written protest (see IRC §6330(d)(1)). 2) Take your case to the U.S. Tax Court (see 26 U.S.C. §7442). 3) If the tax has already been assessed, you can pay the disputed amount and file a claim for a refund (see 26 U.S.C. §7422), then potentially take your case to the U.S. District Court or Court of Federal Claims. It’s important to act within the required timeframes and follow proper procedures.