Republican Sen. John Thune told CNBC the tax rate "structure" in the Senate's reform bill, set to be unveiled Thursday, will differ from the House plan.
The House bill proposes to cut the number of income tax brackets from seven to four: 12 percent, 25 percent, 35 percent and 39.6 percent.
"We do have a different rate structure than what we have today, and we do have a different rate structure than what the House plan has," Thune told "Squawk Box."
He did not provide specifics.
As chairman of the Senate GOP conference, the South Dakota lawmaker is the third-ranking Republican in the Senate.
Thune also declined to comment on whether the Senate bill would delay implementing certain measures, such as the corporate tax cut, saying "that'll all come out later."
A few hours after Thune's appearance, a source told CNBC that the Senate tax plan would delay a corporate tax cut until 2019. On Wednesday, the nonpartisan Congressional Budget Office said the GOP bill would increase the federal budget deficit by $1.7 trillion over 10 years.
"We've looked at different options on that," Thune told CNBC on Thursday, adding he's "happy" with what the Senate has done in regards to the rate structure.
The highlights of the Senate plan will be similar to the House bill, he said.
"We'll take a slightly different approach on a couple of the issues," he added. "But in the end, we all want to get to the same place."
"What we try to do is ensure there's progressivity in the code, that the tax burden is similar to what it is today, and ... the relief flows evenly," he said.
Senate Republicans are preparing to put out their tax plan two days after the GOP took a drubbing in off-year elections.
Democrat Ralph Northam defeated Republican Ed Gillespie in Virginia's hotly contested race for governor, which many analysts viewed as a referendum on President Donald Trump.
In New Jersey, Democrat Phil Murphy won the gubernatorial race against Republican Lt. Gov. Kim Guadagno, who was No. 2 to the unpopular, outgoing Gov. Chris Christie.
Democrats, who did well around the country in other state races and locally, were looking ahead to next year's midterm House and Senate elections with renewed optimism.