Problems began Tuesday when House Minority Leader Stacey Abrams, D-Atlanta, pointed out the plan, which would lower the personal income tax rate from 6 percent to 4.5 percent, worked out to be an increase on the average middle-class taxpayer.
The bill would "flatten" the tax code by eliminating most deductions, such as for charitable giving or interest on home mortgages.
The Joint Committee on Georgia Revenue Structure's approval Tuesday set up a vote in the House. But the bill was in trouble by midmorning Wednesday as rank-and-file Republicans worried about Abrams' new figures and the speed of the process.
By the end of the day, Ralston announced House and Senate negotiators had been unable to come to an agreement and the bill would have to wait until today. But he defended the plan, saying the proposed tax changes would draw new jobs.
It was a frustrating end to a long day for House Majority Leader Larry O'Neal, R-Bonaire, who said the House and Senate members of the joint committee could not even agree to meet.
"We have the votes on this side for responsible, thoughtful tax reform," he said. "It does not appear to me there is a consensus in [the Senate]."
Sen. Jim Butterworth, R-Cornelia, said he was concerned about making such momentous and complex changes in such a short time frame.
Ralston said he believed a tax bill could pass with bipartisan support in his chamber.
"We can talk through issues," Ralston said of Abrams. "We just need that same level of cooperation with the Senate."
Abrams was more reserved, saying she would have to see the legislation, but she noted she was not invited to any of the negotiations despite being on the joint committee.
The bill is the product of a Republican effort last year to reform Georgia's tax system. Legislation created the Special Council on Tax Reform and Fairness. It worked for about six months before releasing recommendations in January that included lowering the personal and corporate income tax rates and shifting taxes toward consumer goods and services.
The joint committee dramatically pared down the list after groups complained about the loss of tax exemptions and the proposed taxing of groceries and services such as haircuts and veterinary services.
But criticism Wednesday coalesced around the income tax, which had been promoted as a tax cut. GOP leaders in the House spent much of the day in closed-door meetings, as the rest of the chamber took recesses and other foot-dragging measures in hopes of finding a resolution.
But the plan kept attracting critics. Members of the Georgia Baptist Convention began calling their lawmakers to complain about the loss of the state deduction for charitable giving.
Ray Newman, state missionary for ethics and public affairs, said he feared the change would result in a decrease in giving to the church.
The Georgia Tea Party Patriots issued a statement opposing the plan as a tax hike on the middle class. "This bill specifically hurts the middle class and taxpayers that make regular contributions to their churches or other charities," the group stated in a news release.
To avoid raising taxes on the poor, the plan gives filers a lump-sum deduction to reduce their taxable income by up to $17,000. But that begins to phase out at $75,000 in federal adjusted gross income for joint filers and is gone at $92,000. For single filers, the deduction is up to $8,500 and phases out between $37,500 and $46,000 in adjusted gross income.
Using numbers provided by Georgia State University economist David Sjoquist, Abrams said the plan leaves middle-income filers paying hundreds more in taxes annually.
To fix the problem, Republicans proposed raising the deduction to cover more filers. One plan would allow filers with incomes of up to $60,000 for single filers and $120,000 for joint filers to reduce their taxable income by $8,500 and $17,000 respectively.
Above those caps, the deduction is reduced, phasing out at $68,500 for singles and $137,000 for families.
That satisfies Virginia Galloway, state director for the conservative group Americans for Prosperity. Galloway, whose group had been critical of the process for months, said she was prepared to formally oppose the bill. She said, "I'm basically for tax reform, but there were some problems."
If raising the income limits for the new state deduction protects middle-class taxpayers, Galloway said she would support it.
The proposed change also appeared to satisfy some House Republicans who were on the fence, but others remained unconvinced.
Using the Georgia State figures, Abrams said that offering a break to the taxpayers who make between $100,000 and $140,000 will cost the state nearly $70 million a year.
"That means to keep this revenue-neutral, as has been pledged all along, we have to come up with a tax increase that generates $70 million," Abrams said.
Ralston shrugged off the concern about an unbalanced approach. "I'm always fine with cutting taxes," he said. If the plan attracts new jobs to the state, tax revenue will not be a problem, he said.
The bill's supporters were trying to get it through the House Wednesday to get a vote in the Senate this week. The delay may mean the Senate would not be able to take up the measure until April 12, the next scheduled legislative day after Friday.
Staff writers April Hunt and Christopher Quinn contributed to this article.