JEFFERSON CITY, Mo. -- Missouri homeowners should have greater protection from property tax spikes if legislation signed Tuesday by Gov. Matt Blunt performs as intended.

The new law seeks to close what Blunt and some lawmakers have described as a legal loophole in Missouri's tax system that has let some local governments reap financial windfalls when property values rise.

It also gives quicker notice to property owners when their taxes are due to go up, and it expands an income tax break available to thousands of low-income elderly and disabled homeowners.

He also was holding ceremonial bill signings Tuesday at homes in Platte City, Mo., and St. Louis and a college in Neosho, Mo.

The legislation, sponsored by Senate President Pro Tem Michael Gibbons, R-Kirkwood, drew widespread support from Republican and Democratic lawmakers alike.

Missouri has more than 2,700 entities that levy property taxes, including school districts, cities, counties, fire and ambulance districts, libraries, public hospitals and others. Property owners pay taxes to each of those based on the assessed value of their homes, buildings or land.

The Missouri Constitution already says that if assessed property values rise by more than inflation -- excluding new construction and improvements -- then local governments are supposed to reduce their maximum-allowed tax rate so that the total amount of taxes they collect remains roughly the same.

But some governments have gotten around the rollback requirement by voluntarily setting their tax rates below their voter-approved, maximum-allowed level.

Gibbons has said about 80 taxing districts in the St. Louis area set their tax levies below their voter-approved maximums. Of those, only about 15 voluntarily rolled back their tax rates when assessed property values rose last year, he said.

The new law, which takes effect Aug. 28, will mandate tax-rate reductions when assessed property values rise significantly -- even if tax rates already are below their maximum.

The law also gives homeowners greater warning of impending tax hikes, allowing more time to either appeal or save money to pay the bill. County assessors will have to provide people notices by June 15 of increased property values and the projected taxes they will owe. That requirement will begin next year for large counties but not until 2011 for smaller counties.

The bill also expands a state income tax break offered to lower-income senior and disabled homeowners from the current $750 to $1,100. Eligibility will be expanded to individuals earning up to $30,000 annually, instead of the current $27,500, and to married couples earning up to $34,000, instead of $29,500.

The expanded tax break is projected to cost the state about $6 million annually.

Lawmakers also attached to the legislation a provision limiting how much the Department of Revenue can charge bulk buyers for copies of vehicle and driver's license records. Some companies use those records to track the history of used vehicles, inform schools and trucking companies when their drivers have received traffic violations, and administer vehicle safety recalls.

The department had charged $1.25 for individual record purchases and just a fraction of a cent for bulk purchases. On May 1, the department raised that to $7 and did away with the bulk discount.

Lawmakers upset about the steep increase responded by capping the agency's fee at one-half cent per record for bulk purchases. By attaching the measure to the popular property tax bill, they virtually assured it would be signed into law.

Earlier this month, a Cole County judge issued an injunction against the department's fee increase for violating Missouri's Sunshine Law, which sets limits on how much government can charge for copies of records.