That new deduction for "two-earner married couples" will take some of the sting out of the marriage tax, but not all of it. (When the IRS last checked--in 1979--it found that 16 million married couples would have paid less tax filing as single people than they did as a married couple; 24 million couples--mostly those with only one income--actually experienced a "marriage bonus.")

The penalty kicks in when the lower-paid spouse earns at least 20 percent of the couple's combined income. But starting in the 1982 tax year, couples will be able to deduct 5 percent of the salary of the lower-paid spouse (for the first $30,000 of salary). In 1983, the deduction will rise to 10 percent. According to the IRS, here is how the change will work for two hypothetical couples earning $45,000, applying both the standard deduction and new lower tax rates.

A husband earns $38,000 and the wife $7,000--and thus is not penalized for being married. Still the new deduction will help. For 1981, the couple would pay $12,232 in taxes; as single people, they would pay slightly more--$12,325. In 1982, their taxes would be reduced by $2,003 to $10,229, filing jointly; they would pay $10,616 if they filed as single people.

Now take a couple where the husband earns $20,000 and the wife, $25,000. For 1981, they'll pay $12,232 as a couple; as two single people, they would pay only $10,020. For 1982, their tax bite will drop $2,257 to $9,975. The marriage penalty won't disappear, however. As single people, they would pay only $8,454.