THE HOUSE AND SENATE, with a fine sense of prioties, have just found time to rush through a little tax break for a very special interest group - themselves. The bill, passed by the House June 6 and by the Senate Thursday, says that "not state" may tax the income of any legislator who lives there while attending sessions of Congress. "No state" in this context means Maryland, the only area jurisdiction that has ventured to suggest that the 125 to 150 members of Congress who abide there for much of the year should pay income taxes like everyone else.

Before anyone weeps for the poor legislators whose incomes get taxed here and also back at home, it should be noted that Maryland allows reciprocal credits with other income-taxing states. The congress-men who owe the most to Maryland, therefore, are those form the nine states that have no income tax.

We recognize that it can be a strain on any citizen to have to pay suburban property taxes, sales taxes and a state income tax besides, especially when the tax bill is going up because one's income has just jumped from $44,600 to $57,500. What these particular citizens emphasize, though, is not the income but what they like to think of as the principle involved. They argue that federal legislators come here out of necessity, not choice - as if being in Congress were some form of involuntary servitude. Moreover, the Washington area should be grateful for their presence, they maintain; it's hard for them to see why Maryland is so churlish as to deny them the exemption that Virginia law permits and that the District's code, written by Congress, also (oddly enough) provides.

But Maryland has decided otherwise - and Maryland should be free to make that judgement for itself. That's what President Ford maintained when he vetoed a similar bill last year. "It is one thing," Mr. Ford's veto message said, "for a taxing jurisdiction voluntarily to exempt members of Congress from its income laws and quite another for Congress to mandate a federal exemption on a state income tax system . . . Such federal interference is particularly objectionable" where state revenues help to support local public services that all who live there "use and enjoy." That sums it up pretty well, as far as we we're concerned. Assuming this bit of congressional self-help reaches President Carter's desk, he can save himself some time by simply dusting off his predecessor's veto message and sending the bill back again.