Senate Republicans moved to patch up their tax plan on Friday morning, after a setback forced them to delay a vote hours before they hoped to pass the bill on Thursday night.

Senators moved to rework the legislation on Thursday night and Friday morning. The next in a series of roll call votes is set for 11 a.m. on Friday, Senate Majority Leader Mitch McConnell said. Republicans had previously hoped they could pass a plan by late Thursday or early Friday.

The GOP effort got a boost Friday morning, when Sens. Ron Johnson, R-Wis., and Steve Daines, R-Mont., said they would support the bill after securing a bigger tax break for pass-through businesses. They were two of the last GOP holdouts.

A hiccup Thursday left the GOP scrambling to tweak its bill and win over skeptical senators. The delay did not necessarily mean Republicans will lack the votes to pass the legislation on Friday.

On Friday morning, Senate Majority Whip John Cornyn, R-Texas, called holdout Sens. Bob Corker, R-Tenn., and Jeff Flake, R-Ariz., the last two senators who need to get on board. It is unclear where that leaves holdout Sens. Susan Collins, R-Maine, and James Lankford, R-Okla., who have not yet committed to supporting the proposal.

Senate Finance Committee Chairman Orrin Hatch, R-Utah, on Friday said he believes Republicans have the votes to pass the bill. Corker told NBC News on Friday that he thinks the GOP can approve it even without his vote.

The Senate parliamentarian ruled Thursday that a fiscal "trigger," important to winning deficit-wary Corker's support for the GOP plan, will not work under Senate rules. Republican senators are now looking to find new ways to address the concerns of Corker, a so-called deficit hawk Republican from Tennessee.

"It doesn't look like the trigger is going to work, according to the parliamentarian," Cornyn told reporters, according to Politico. "So we have an alternative, frankly: a tax increase we don't want to do to try to address Sen. Corker's concerns."

The setback came shortly after the nonpartisan Joint Committee on Taxation estimated that the plan would fall $1 trillion short of paying for itself, even after economic growth is taken into account. While GOP Senate leaders like Cornyn and John Thune of South Dakota downplayed the findings, Corker pushed for a way to make up for the budget hole.

Sen. David Perdue of Georgia said his fellow Republicans are considering future tax increases not linked to any trigger as part of the bill. Senators are reportedly mulling small increases in the corporate tax rate after an initial, dramatic reduction to 20 percent.

Lawmakers are weighing whether to make corporate tax cuts in the plan expire in year six or seven, Reuters reported, citing a Republican senator and an aide.

Shortly before the parliamentarian's ruling, Corker, Flake and Johnson delayed voting on a measure to advance the bill as they talked with GOP leaders on the Senate floor. After the conversation, the senators voted to push ahead.

Other senators like Collins, Marco Rubio of Florida and Mike Lee of Utah are seeking concessions that the GOP may need to raise additional revenue to satisfy.

Republicans, who hold 52 seats, can only lose two votes and pass the bill if all Democrats and independents oppose it. They only need a simple majority, including a tiebreaking vote from Vice President Mike Pence, under special budget rules.

As the bill stands, it makes many individual tax cuts expire within a decade to comply with budget rules. The corporate tax rate reduction to 20 percent from 35 percent was expected to be permanent.

If the Senate passes its bill, lawmakers then plan to go to a conference committee with the House. The chambers will have to strike an agreement on a final bill.

Both the House and Senate would have to approve the new legislation to send it to President Donald Trump for his signature.

— CNBC's Ylan Mui Reuters contributed to this report.