Senate negotiators offered up $26 billion in additional revenue yesterday to keep their tax-revision bill from increasing the federal deficit or penalizing middle-income taxpayers, but their House counterparts objected to many of the limits on tax breaks the senators had chosen.

"My conclusion is, they haven't really faced yet the reality of what has to be done," said Rep. Richard A. Gephardt (D-Mo.). "I don't think they have $26 billion or anything like it."

Although the House has not officially rejected the Senate offer, the strength of the objections seemed to indicate that senators will have to find other revenue sources to make the bill "revenue-neutral." Until it is, conferees cannot begin the process of deciding which deductions they wish to retain in the final tax-overhaul bill.

Without the laundry list of tax increases agreed to during a private session, the Senate bill -- the starting point for the conference committee's drafting efforts -- would bring in $21.2 billion less in federal revenue from 1986 to 1991 than current law.

Items that senators added to the other limits on deductions in their bill include: closing a loophole in the bill's repeal of the deduction for nonmortgage interest that lets people borrow against their homes without limit (raising $3.5 billion); limiting use of tax-exempt bonds ($2 billion); cutting the yearly contribution limit to tax-deferred 401(k) plans from $7,000 to $5,000 ($2 billion), and including a scheduled Treasury Department adjustment in the tax tables used to calculate the sales-tax deduction ($3 billion).

"It is made up of lots and lots of small pieces," said Senate Finance Committee Chairman Bob Packwood (R-Ore.). The list was not made public. But like many documents important to the fate of tax-overhaul, it was leaked to lobbyists, who gave it to reporters.

House conferees from both parties noted that many of the items on the list were not drawn from either bill. "They've gone outside the scope of the conference a little early," said Rep. John J. Duncan (R-Tenn.). "You usually save that till later."

Rep. Marty Russo (D-Ill.) said, "In my personal view, there are things that don't make any sense."

Even if the Senate can satisfy House objections, conferees will need to find as much as $50 billion more if they decide to resolve all of the various objections to the Senate bill. House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.) said yesterday that restoration of deductions for Individual Retirement Accounts for lower- and middle-income taxpayers is "pretty well agreed to."

House Democrats have insisted that the final bill provide as much tax relief for those earning between $20,000 and $40,000 per year as the House bill would.

Another objective of tax conferees is moving the effective date of the tax-rate cuts in the measure up six months to the date when deductions would be limited -- a step that would cost $29 billion in revenue. Conferees from both chambers say they want to get rid of "the stagger," as the delay in the rate cuts has become known.

"Now we're going to be faced with the really tough questions: What we're going to do and how we're going to pay for it," said Sen. John C. Danforth (R-Mo.). "It comes down to a question of the rates versus the stagger, or rates versus IRAs."

Packwood said later that although "there are still some more corporate loopholes that can be closed," it may take higher rates to offset the cost of moving the tax cut forward.

Other members of the conference also predicted yesterday that the top tax rate in the final bill probably will be higher than the 27 percent that legislators have agreed to use as a starting point.

By accepting the Senate's rate structure of 15 percent and 27 percent for individuals and 33 percent for corporations, House conferees say they have put the onus on senators to come up with the revenue to pay for restoration of deductions while keeping rates low. Several pointed out that if senators needed ideas, the House bill includes $105 billion over six years in new corporate taxes.