Chief Appraiser Phil Hogsed said about 30,000 more notices will be mailed this week. That means notices are going to nearly 60 percent of Cobb's 230,158 homes, and the vast majority are decreases in value.
In March, Hogsed predicted that even more notices would be sent.
A state law passed last year prohibits increases to residential property - unless the property has been improved in some way - through 2011.
Original estimates forecast a 9 to 11 percent reduction in the 2010 tax digest, to $26.9 billion. The digest is the value of all property in Cobb County, and city and county leaders use it to determine how much tax revenue to expect, and thus to set their budgets.
The 2009 digest was $30.8 billion, the first year in memory that it had gone down. In 2008, the digest was $31.2 billion.
Hogsed said he would not know exactly where the 2010 digest stands until later this month, though as of now, the residential portion is down about 10 percent, and commercial is down about 3.5 percent.
The cities and other taxing authorities must receive the digest by July 1.
Homeowners in Austell and Powder Springs will likely see the largest declines as a result of the September 2009 floods, Hogsed said.
And 12,895 homeowners filed a return - the first step in disputing the assessors' evaluation - by the April 1 deadline. Last year, 9,324 homeowners filed a return.