Property owners across Harris County received their 2014 property value notices earlier this month, and both the Harris County Appraisal District and area tax agents are anticipating a substantial increase in protests to have those values lowered.

Property values—which factor into how much property owners pay in property tax—are determined each year by HCAD through a process set by the Texas State Constitution. Appraisers with the county determine the value of all commercial, business and residential property starting in January based on market value. The average appraisal rose by nearly 17 percent this year, which HCAD officials attribute to Houston's red-hot real estate market.

John Osenbaugh, an independent property tax agent in the Houston area, said HCAD appraisals overshot the marker in many areas.

"In many cases, the subdivision data you get from [Houston Area Realtors] and MLS do not support the HCAD's assertion as to value increase in multiple neighborhoods," he said. "These numbers support a 6–8 percent increase, but not the 17 percent increases people have been seeing."

Osenbaugh attributed some of the discrepancy to home values being artificially inflated while they are on the market, which he said can have an affect on the values of comparable homes in the neighborhood.

"Usually a house has been dolled up with cosmetic work prior to sell," he said. "The district has gone to the top end and perhaps stretched it even further. The original idea was to shoot a little below that. They've been overaggressive and they've not really followed the original intent of the district."

The problem is also not limited to HCAD, Osenbaugh said. Appraisal districts in Fort Bend and Montgomery counties are also seeing sizable increases.

"Both have been overly aggressive in trying to chase the market and have overshot in multiple neighborhoods I've been dealing with," he said.

HCAD officials say values reflect one of the strongest seller's markets in the nation, with housing inventory at an all-time low at the end of last year. Chief Appraiser Sands Stiefer has pointed out that valuations are statistically accurate, citing 2013 records from the Texas Comptroller's Office, which showed appraised residential property at 97 percent of market value, commercial real property at 101 percent and business personal property at 99 percent.

Protests can be filed electronically, by mail, using an official protest form or through a hired agent. Protesters make their case to the Appraisal Review Board, which is made up of an independent panel of citizens.

For people who are unsure if their appraisals should be protested, Osenbaugh recommends looking to www.har.com to get a glimpse of home values, means and medians by neighborhood. He said most people file online using iFile, but also cautioned against using the county's iSettle service, which he said only provides a "token decrease."

Property owners have until June 2 to file protests.