For most Americans, paying taxes to the Internal Revenue Service is an unpleasant experience. But it is even more unpleasant when honest taxpayers realize that they are carrying the burden for the estimated 20 percent who under-report, fail to report or don't pay.

This huge burden, called the tax gap, is the difference between taxes that are owed and what is actually paid each year.

The tax gap, which has been estimated to be about $350 billion a year by the IRS, is shocking — or should be — to every honest taxpayer, because they are making up the difference for the tax cheats.

The extra taxes that honest taxpayers must now pay was estimated at an average of $2,680 per household in 2001. This year, no doubt, it will be larger.

Clearly, lower-income people are paying a smaller surcharge, while higher-income taxpayers are hit with premiums for the tax gap that go well above the $2,680 average.

The size of the tax gap is stunning, especially when it is noted that if all taxes due were actually paid, the annual federal budget deficit would disappear. There are other examples of what those unpaid taxes could do, such as pay for the $125 billion that Congress has designated to pay for Hurricane Katrina relief, with enough money left over to fund federal education programs — for three years.

The scope of the tax gap is troubling because it suggests that millions of Americans are comfortable cheating — and apparently have little fear of getting caught by the IRS.

Because the income tax system in the United States is partially based on honest reporting of income, the growing practice of cheating threatens the entire system. If cheating grows and becomes more common, otherwise honest taxpayers might be tempted to underreport their income or exaggerate their deductions to avoid paying their fair share. At that point, the entire system is in danger of collapse.

As one taxpayer advocate noted, "nobody wants to be a tax chump."

More IRS audits would seem to be the solution, but most experts agree that increasing audits alone cannot erase the tax gap. It can help, so already the IRS has increased the audits it conducts, with the chance of being audited nearly doubling since 2001. Tax returns of multimillionaires are receiving special attention, as they probably should. The IRS also has begun using private collection agencies to boost collections.

There are proposals for more third-party reporting of income, including stock brokerages, which would be required to report capital gains related to stock sales. There even are proposals to mandate reporting of income from Internet sales, such as eBay, where an estimated 700,000 make their living.

Simplifying the tax code also would help, because at least some of the tax gap is due to unintentional underpayments casued by the needlessly complex federal income tax code. A simplified tax code would also help in the area of fairness, because it's widely known that powerful special interests have long had targeted tax breaks written into the tax code by compliant lawmakers.

With tax compliance estimated at about 80 percent, it's in the best interest of most Americans to support serious efforts to close the tax gap. The White House and the Democrat-controlled Congress are both proposing ideas to collect the appropriate taxes from the 20 percent of individuals and businesses who are now cheating, or simply underpaying.

It's an issue of money, in terms of the federal budget, and also an issue of fairness. From both perspectives, the massive tax gap cannot be tolerated. The 80 percent who pay their fair share should support efforts to get the other 20 percent to do likewise.