THERE USED TO BE no doubt what was meant by a tax increase. A citizen was about to be separated from his money. But life and language both have become more complicated. The White House and congressional budget negotiators who wrapped up their work a week ago felt it necessary to introduce a new distinction. No longer do you have just income vs. sales taxes, federal vs. state and local, progressive vs. regressive. You now have hard vs. soft.

That is, of course, a euphemism for true vs. false. The budget agreement, in calling for $9 billion in tax increases, specifies that they must be of the hard variety. There are similar phrases and understandings aimed at circumventing marshy spots on the spending side. The resort to illusions in these matters has become so common that it is no longer enough just to create your own; to win you must also anticipate and nip the other side's.

Thus the other day House Ways and Means Committee Chairman Dan Rostenkowski issued a statement warning obliquely that he intends to drop in conference a provision in both the House and Senate Finance Committee bills that would raise an extra $1.8 billion this fiscal year. The objection is that this provision would not really increase taxes, just advance some payment dates to increase revenues artificially this year only. But the administration had wanted it in the eventual bill, and still does. The more of the $9 billion that is illusory, the less has to be real, and the administration opposes some of the larger real increases Congress is considering. But Mr. Rostenkowski, who had already been forced to accept a smaller tax increase than he wanted, said no.

The spending fight is more familiar. Here the Republicans are the apostles of purity, and, at least as to domestic spending, the Democrats are doing some of the cheating. The budget agreement anticipates some of this as well. Thus Mr. Rostenkowski's Ways and Means Committee had already agreed to keep Medicare spending, over which it also has jurisdiction, about $1.5 billion below the level it would otherwise attain this year. A third of this cut was to be achieved by a gimmick, not a cut in payments but a slowing down, so that some would fall into the next fiscal year. It was finally agreed that Ways and Means could keep the fake cut if it would add an additional $500 million that was real.

So also with the agriculture committees. They had earlier been ordered to cut about $1 billion from the spending under their control, and had done it almost entirely by fanciful accounting. The new agreement calls again for about $1 billion, but says this time it has to be in price supports -- all wheat, no chaff. That would be a major reversal, and an important step in the right direction.