FAR and away, the greatest shift in the tax burden under the tax-and-entitlements bill passed last week is for the working poor, who will collect substantially greater tax refunds by 1996 under the bill.
Altogether, about 16.6 percent of families that file tax returns, all of them with earnings below $27,000 a year, benefit from a tax cut in the Clinton economic plan that comes in the form of an expanded Earned Income Tax Credit.
For 82.2 percent of all American families, income tax rates will not change at all, according to figures assembled by H&R Block, the tax-service company.
The slated increase in income tax rates will apply only to the thin slice of the population - the highest-income 1.2 percent of households. The current top marginal tax rate of 31 percent will rise to 36 percent for taxable income above $140,000 for married couples filing jointly. For singles, the new rate of 36 percent takes effect at $115,000 in taxable income.
In terms most people think of as income - the figure before subtracting tax deductions - these figures translate to about $180,000 for married filers and $140,000 for single taxpayers, according to the United States Treasury Department.
All those with taxable income above $250,000 will pay a 10 percent surtax, raising the top rate to 39.6 percent. In gross income, that means a level of about $320,000.
These tax increases are retroactive to Jan. 1 of this year. But the Treasury Department will allow people to spread payment of their higher taxes this year over their next three returns.
The affluent will face another kind of tax increase as well. A Medicare tax of 1.45 percent is now levied on all earnings up to $135,000. That cap will be lifted next year, so that all earnings are subject to the tax, without upward limit.
The tax chart on this page shows what will happen to a family's taxes assuming that they will pay the Medicare tax on all earnings above $135,000 for the first time. But a family with two highly paid earners may already be paying the tax on joint income as high as $270,000.
The other major income tax hike affects affluent retirees, as a greater share of Social Security benefits becomes taxable. For seven of every eight Social Security recipients, income taxes will not change at all.
The formula for whose taxes will rise is one that only an accountant could love. For married couples filing jointly, most of those whose gross incomes (not including Social Security) plus half their Social Security benefits add to $44,000 or greater will pay taxes on 85 percent of their Social Security benefits, up from 50 percent. For single taxpayers, the trigger point is $34,000.
Because this tax hike works by adding to taxable income, it has its steepest impact on people who will see their Social Security benefits now jut up from the 15 percent bracket into the 28 percent tax bracket.
The tax chart on this page assumes that those older couples affluent enough to be affected by this change are receiving the full $14,440 Social Security benefit. It also assumes about $16,000 in tax deductions, equal to a standard deduction, two personal exemptions, two exemptions for age, and several thousand in tax-free pension or other income.
The one tax that will have a direct effect on nearly every American family is not linked to income at all - the 4.3-cent-per-gallon gasoline tax. This move raises the federal tax on a gallon of gasoline tax from 14.1 cents to 18.4 cents.
The Treasury estimates that this tax will cost the average family $3 a month, or $36 a year. The conservative Tax Foundation estimates that the average family will pay an extra $76 a year.
It depends entirely, of course, on how much gas a family burns. The Treasury estimate assumes, at about 20 miles per gallon, that the average family drives 1,396 miles in a month, or 16,752 in a year. At the same mileage per gallon, the Tax Foundation figures assume 2,946 miles every month, or 35,349 miles a year.
This tax will have a regional impact, since most people drive much further in Wyoming, Georgia, Montana, and Missouri than in Hawaii, New York, Pennsylvania, or Utah, according to Federal Highway Administration data. But the direct impact on families lies entirely on their own consumption.
Beyond these points, the tax picture grows much more complicated. Many tax breaks and some special taxes are shifting - from the shrinking deduction for business lunches to the canceling of the luxury tax.
The best news, however, is for the 1 family in 6 that is among the working poor, some of whom will be receiving $3,370 in tax refund by the year 1996, when the new program is fully in effect. This amounts to a 40-cent tax credit for every dollar earned up to $8,500.