AUSTIN — Republican Gov. Greg Abbott signed a bill into law that county appraisers warn could wreak financial havoc on local budgets by letting property owners retroactively appeal years-old tax bills, once cities and school districts have already collected and spent the money.

Reining in property tax growth for homeowners has been a major goal of Abbott’s this year. But critics say this new law will especially benefit businesses and companies with extensive land holdings by making it easier for them to fight their property tax bills in court.

“It’s difficult when the state claims to want to protect homeowners and engage in this type of subversive politics,” said Michael Amezquita, chief appraiser at Bexar Appraisal District, in a statement. “This will benefit the largest commercial owners to the detriment of homeowners.”

Abbott didn’t respond to questions about the legislation, known as House Bill 380. Rep. Charlie Geren, a Fort Worth Republican who filed the bill, disputes appraisers’ analysis. The measure simply gives people an opportunity to correct procedural mistakes in a protest, he said, so each challenge can be considered on its merits.

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Under current law, when a person or business appeals a tax bill, county officials can deny the appeal for any number of procedural mistakes or missed deadlines. The new law will give property owners the opportunity to correct those mistakes and start over.

“It puts another tool in the tool box for the property owners,” Geren said. The law takes effect in September, and its scope will likely depend on how courts interpret the change. District judges will have the power to give property owners a chance to fix mistakes they make on a protest, which appraisers have said could include failing to file it in a timely manner.

The effects won’t likely begin until next year, said Jim Popp, a prominent Austin tax attorney, who has said the legislation could have been written more clearly. “It will be a slow process to figure out what it really means,” he said of the new law.

“There's deadlines for filing your protest, there's deadlines for filing your lawsuits and I think those deadlines are important for finality in the system,” Popp said. “The court could read it to replace those deadlines. I'm not saying they will, but the interpretation given by the appraisal districts is reasonable.”

If the law opens the door to protesting values from years past, the result could be financially ruinous for small counties where one or two large properties make up a substantial portion of the tax base, Kirk Swinney, an Austin-area attorney who represents roughly 70 appraisal districts, has said.

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The measure was widely supported by tax agents, who file protests on behalf of homeowners and large businesses, and by Texas Realtors, a trade group. Neither group immediately responded to a request for comment.