Under current law, the willful failure to pay taxes is a misdemeanor. You could go to jail for up to a year and pay a maximum fine of $25K (for individuals, $100K for corporations) for each year you fail to file a return. There is a proposal in the new budget to increase the penalty for repeated failure to file a tax return:
Any person who willfully fails to file tax returns in any three years within any five consecutive year period, if the aggregated tax liability for such period is at least $50,000, would be subject to a new aggravated failure to file criminal penalty. The proposal would classify such failure as a felony and, upon conviction, impose a fine of not more than $250,000 ($500,000 in the case of a corporation) or imprisonment for not more than five years, or both.