RIGHT ABOUT NOW, millions of taxpayers must have some ideas for improving the Internal Revenue code and in the process fattening their own deductions a bit. But only 535 taxpayers, those in Congress, can actually write their self-serving thoughs into the law. Some House members are trying to do just that. They have brought out the old two-homes argument again to justify giving themselves a tax cut of more than $2,000 per year, on top of the special break they already enjoy.

As the lawmakers see it, the problem is that the law doesn't fit with their jobs. Their work entails special expenses - maintaining a home back home and one here, transporting their families and the like. If Congress met for a few months per year, their rooming and boarding here would qualify as business expenses out of town - that is, away from their districts - and would be deductible on Form 1040, line 23 (with Form 2106 attached). But Congress stays here nine months per year or more (except during "district work periods," one of which is going on now). Under normal IRS rules, an employee who stayed in Washington that long would no longer be away from home for line-23 purposes; his "tax home" would be here.

If senators and representatives abided by the general rule, they could deduct the costs of going back to their states on business - but that arrangement is politically unpalatable. It smacks too much of being captured by Washington and pulling one's stakes out of the old grass roots.

So what to do? One theoretical option is to swallow hard and bear the costs. Congress rejected that a while ago by amending the law to let members keep their "tax homes" at home and deduct up to $3,000 for living expenses here. Now some House members want to raise that tax-free allowance to $50 for every day that Congress sits. Let's see . . . last year the House met on 149 days. That times $50 is $7,450. Subtract the $3,000 they already deduct; multiply by 50 percent (their approximate tax bracket) to get a tax break of $2,225. (In 1977 the House sat even longer: 174 days. You work that out.)

There is another way to look at the whole matter, and it's one most taxpayers may prefer. That is to set aside all of the philosophical and practical and arithmetical arguments about where members of Congress live or should call home, and simploy think about dollars and sense. Representatives get paid 57,500 dollars per year. They get it for a job that no one ordered them to take - and one whose terms should have been plain when they applied. If they need more dollars to support their families and homes, they should try to persuade their employers, the voters, that a pay raise is in line. Common sense sought to tell them that finagling with the tax code doesn't sit too well with the people back home.