WHEN CONGRESS passed a $350 billion tax bill last year, lawmakers managed to cram the measure into that preset spending ceiling by scheduling the most popular tax breaks to expire at the end of this year. That gimmick made the cost of the 10-year bill look lower, though no one believed that the cuts would be allowed to evaporate. And, of course, they won't. The House has already approved extensions, and the Senate is expected to take up the issue this week.

We have no quarrel with extending the cuts, provisions aimed at helping the middle class by increasing the child tax credit to $1,000 per child, easing the marriage penalty and expanding the 10 percent tax bracket. But senators need to remember that they balked at a tax cut in excess of $350 billion because they considered anything larger unaffordable in light of record deficits and looming costs. Now, they are poised to enact another cut that would cost an additional $120 billion over five years. If lawmakers want to extend the tax cuts, they should find a way to pay for them. If they don't have the will to do that -- and there are ample ways -- they should at least contain the fiscal damage by keeping the extension to a year or two.

The sanest way of paying for the tax cuts is the least likely in the current political circumstances -- trimming back the existing breaks gratuitously lavished on the wealthiest Americans. But that's not the only possibility. The Senate has already assembled a package of $130 billion in tax savings over the next 10 years, mostly by cracking down on corporate tax shelters. Unfortunately, that money is going to another cause: paying for new corporate tax breaks as part of a bill that was supposed to allay the effects of a trade ruling. There's a skewed set of priorities.

The question of priorities leads us to the dodgy procedural device by which the middle- class tax measure is being brought to the Senate floor. Instead of being brought up as a free-standing bill -- which would expose it to amendments -- the cuts will come to the floor in the guise of a "conference report" on a bill to expand the child tax credit for the working poor. That dormant measure was debated after a storm of embarrassing publicity about the poor children that last year's tax bill left behind, but it was quietly abandoned when House Republican leaders insisted on a bloated bill that would have heaped extra benefits on lots of rich children too.

Now, though, the "conference report" on the measure has become a convenient vehicle for dealing with the middle-class tax cuts in a way that would bring them straight to the floor on a take-it-or-leave-it, no-amendments-allowed basis. This is an outrage, but it's even more outrageous that there is some behind-the-scenes rumbling about dropping the extra help for poor kids that was the very impetus for the original bill. The House version of the bill would provide that modest boost but at a cost: increasing the availability of the child tax credit for those at the upper end of the income scale, so that a family with three children and income of more than $300,000 would still be able to claim a partial credit. Wealthy Americans don't need extra government subsidies to raise their kids. If Congress wants to help the middle class, it can do so in a way that's limited and affordable.