THIS COUNTRY RUNS to extremes. Three years ago we had a President who wouldn't pay his full share of taxes. Now we have one who insists on paying too much.

There is a disquieting overtone to President Carter's grand gesture in presenting the Internal Revenue Service with $6,000 to which, under the law, it is not entitled. Taxes are the dues that we all pay for our memberships in that great common enterprise the United States of America. The amount paid ought not be a matter of gestures, which, after all, can cut two ways. For every person who doesn't think he pays enough, how many do you suppose there are who think they pay too much? It was a generous act on his part, you could quite accurately say. But you could just as accurately call that $6,000 a gratuity, a large tip offered as one of the obligations of rank.

Mr. Carter's income last year was $54,934, and he is certainly right when he says that people at the level of income ought to pay some tax. But his tax liability was zero because of credits that he got on investment in the family's peanut business. He chose to pay the $6,000 because if represents 15 per cent of his income after the usual deductions. Congress last year set 15 per cent as the minimum rate for taxpayers - although, in its infinite complexity, the tax code does not apply to certain benefits, including the investment credit.

That, of course, is where the troubles lies. If it is distressing to have the President's taxes left to gestures and gifts, that's certainly better than having the President contribute nothing. The discovery that the President paid no taxes would hardly strengthen other citizens' faith in the basic fairness of the system. Nor would it have helped Mr. Carter's public standing - as Ronald began could testify.

The basic defect here is not in the President's judgement but, rather, in the tax code. Mr. Carter's case is not unique. Several months ago the Treasury Department published an analysis of the 1974 tax returns showing that 3,745 of those returns reported incomes over $50,000-plus income range. Gifts to the government by prominent people do not constitute a satisfactory solution. There's a better one available -broadening the minimum tax requirement - in the tax-reform bill that the Carter administration is now drafting.