"We've seen a huge surge in -- really, I'll just call them con artists, that's really what they are," said San Francisco assessor Phil Ting.
Ting and his counterparts from Alameda and Marin counties are warning about letters that look like official documents homeowners are receiving estimating their property's assessed value and offering to help get it reduced for a fee.
In fact, a property tax review is something all county assessors do for free and most are doing it automatically because of the declining market.
"Some of those companies are saying, 'Do you really think your assessor will give you a fair shake when it comes to the correct evaluation?' And I think that we do, and the 99,000 reductions that we lowered in Alameda County testify to that," said Alameda County Assesor Ron Thomsen.
The warning comes too late for homeowners who have fallen for the sales pitch.
"I'm a single mom, I am a working single mom. That's probably one of the reasons I got trapped," said homeowner Glynis Brooke.
Starting January 1 a new law, authored by assembly member Ted Lieu, calls for criminal and civil penalties on solicitors -- especially those whose letters look like authentic government documents.
"If they made it so it's not an official government looking letter, they might be able to skate on the law as long as they're actually providing a service. However, I think these assessors will tell you that people don't call them and they are just giving this money, and these companies don't do anything, they take the money and run," said Assm. Ted Lui, D-Torrance.
The county assessors aren't sure how many victims there are, certainly thousands. Solicitation letters have been sent to property owners all over the state.
The assessors say the con artists are trying to scam as many people as they can until the new law takes effect.