Taxes are filed in the US largely on the honor system. The IRS "matches" a number of major documents such as W-2s, mortgage interest, interest and dividend income, etc., but taxpayers voluntarily report most information. Some taxpayers play the "audit lottery" by reporting unsupported information on their tax return (let's say overstating charitable deductions) and just cross their fingers that they will not get audited. What is your opinion of those who play the audit lottery? Would you ever turn in someone (whistle-blower) who you knew for sure was cheating on their taxes? Or do you feel that someone's tax return is just between the citizen and the IRS and you would not get involved?