AUSTIN – A coalition of small-business groups on Thursday launched an effort to revamp the state's new business tax even though the first payments under the tax aren't due until next month.

Arguing that the Legislature miscalculated the impact on thousands of small businesses across Texas, the National Federation of Independent Business and four associations said they will seek several changes in the business franchise tax when lawmakers convene next year.

"It is by far the most complicated, convoluted system of taxation ever devised by man," said Will Newton, executive director of NFIB-Texas. "It's hard to figure out, hard to plan for and hard to pay."

Mr. Newton said his group has heard countless stories about "the incredible amount of tax increases" for small-business owners this year.

One of those was from an electrical contracting business in Forney, whose owner discussed his tax situation during a briefing of the coalition on Thursday.

Keith Bell, president of Intex Electrical Contractors Inc., said his tax payments have shot up more than 13-fold this year, and he estimated he will have to pay about $51,000 under the new franchise tax. Under the old franchise tax last year, his company paid about $3,900.

Although businesses were promised property tax reductions that would offset their business tax hikes, Mr. Bell said his property tax savings amounted to just $3,500.

"I don't have a problem paying my fair share, but I don't think that big of an increase is fair," he said. "The Legislature made a mistake, and they need to fix it."

Kurt Summers, president of Austin Generator Service, called the new tax "a boondoggle that has nailed small businesses to the wall." He also cited a huge increase in his state taxes.

Supporters of the new tax, such as Dale Craymer, chief economist for the Texas Taxpayers and Research Association, have argued that businesses are "far better off" with the new system than they would have been had the Legislature done nothing. If the tax system had not been revamped two years ago, property taxes would have soared and overall business taxes would be much higher, he said.

The new levy was approved by the Legislature in spring 2006 as part of a massive tax reform package that lowered school property taxes by a third and replaced the revenue with higher taxes on businesses and smokers.

An estimated 900,000 businesses are subject to the business franchise tax – also called the margins tax – but fewer than a third are expected to actually write a check to the state because of exemptions for businesses that have gross receipts of less than $300,000 a year or that would have had a total tax of less than $1,000.

Sole proprietorships are not subject to the tax.

Most businesses will pay a tax of 1 percent of gross receipts – after taking certain deductions – while retailers and wholesalers will pay 0.5 percent of their gross receipts.

The five business groups are seeking a half-dozen key changes in the law, including a tax exemption for all businesses with gross receipts under $1 million a year. Lawmakers rejected that idea in their 2007 session.