Internal Revenue Service officials pushed legislation through Congress Monday requiring all taxpayers to add a gratuity of 'no less than 12 percent' to 1997 income-tax payments. 'We work hard,' IRS director Hiram Stockton said, 'and, apparently, many taxpayers don't realize that IRS agents rely on tips to make ends meet.' The new era of mandatory tipping is expected to be a boon for IRS agents, many of whom say they could not subsist on the voluntary, often-meager tips of the past. 'We process forms in a timely fashion, send out refunds promptly, and always stop by each taxpayer's home to ask, 'Is everything all right here? Can I get you anything else?' as often as we can during the tax-filing season,' IRS processing agent XJRC-1582H-GY3-5 said. Families with eight or more dependents will have a 20 percent gratuity automatically added to their tax bill. Failure to tip will result in a $50,000 fine and/or up to 15 years in federal prison. 