Once again, proposals for a flat rate income tax system are being considered by the Utah Legislature. The idea came close to being adopted in 1987, only to falter because of concerns over the fate of charitable deductions. But there are some advantages to a flat tax if such issues can be satisfied.

In some respects, Utah already has a de facto flat tax, although not by design. Because the state income tax tables have not been adjusted for inflation since the mid 1970s, three quarters of all Utahns now find themselves in the top bracket, taxed at a rate of slightly more than 7 percent.Yet there are problems with the system. The present state income tax structure is somewhat progressive - meaning those with bigger incomes pay a larger percentage of their income in taxes - but only slightly so.

Most other Utah taxes, such as sales taxes, excise taxes and real estate taxes, tend to be regressive. For example, the Utah Foundation notes that people earning $10,000-$15,000 a year pay 4.4 percent of their gross income in sales taxes while those earning $50,000 a year pay half that - 2.2 percent.

When all state and local taxes are lumped together, the average tax burden is fairly constant, peaking at about 8.9 percent in the $35,000-$40,000 range. After $100,000 a year, the tax burden as a percentage of income declines steadily as income rises. Most flat tax proposals would alter those numbers.

Three measures prepared for the Legislature by Rep. John Valentine, R-Orem, offer different scenarios for a flat tax. All would be revenue neutral - not providing any more and any less revenue to the state than under present tax systems. But the tax burden would be readjusted so that some middle-class families would pay a little less and those with larger incomes would pay a little more.

Valentine's three bills offer the following options:

- HB338: A true flat tax of about 4 percent, with no deductions or write-offs for federal taxes, charitable gifts, home mortgage interest, or anything else.

- HB337: A flat tax rate of 5.25 percent that allows personal exemptions and charitable gifts to be deducted.

- HB336: A flat tax of 5.41 percent that allows deductions for personal exemptions, charitable gifts and mortgage interest.

At least nine variations and permutations on these themes were prepared by the Legislature's Revenue and Taxation Committee and forwarded to the Tax Review Commission. Each would have affected taxpayers in different ways.

Of the three measures sponsored by Valentine, the third option seems to be the most reasonable. Any tax system that did not allow deductions for charitable giving could cripple privately-funded community services like the United Way and perhaps destroy the already struggling arts, such as ballet, symphony and theater organizations.

If tax deductions for charitable gifts were denied, taxpayers would find themselves - one way or another - having to make up at least some of the losses to human services from private donations.

The traditional practice of allowing deductions for interest on home mortgages grows out of government desire to encourage home ownership. Such ownership promotes community stability and family-centered values.

Certainly, any flat tax that allows exceptions leaves itself open to pressures for other exemptions that eventually might undermine the entire flat tax concept. But the values to be gained from allowing some important deductions clearly outweigh that potential problem.

Certainly, some revamping of the tax system needs to be considered. Any income tax structure that has remained essentially the same for more than 15 years could use, at the very least, some adjusting.