MARIETTA — Officials are expecting Cobb’s 2012 tax digest to decline about 4 percent, but County Chairman Tim Lee vowed that such a decline would not result in another property-tax increase this year.

Meanwhile, Chief Appraiser Phil Hogsed is preparing to send assessment notices in coming weeks for each of the nearly 250,000 parcels in the county. The vast majority of those, about 230,000, are residential properties.

The tax 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 to set their budgets.

County Chairman Tim Lee said the county had expected another year of reduced values.

“We planned for it last year in our budgeting, and as a result it won’t have any impact on our operations,” Lee said. “There absolutely will not be a tax increase this summer.”

Lee also insisted there would be no furloughs or layoffs of county employees in the 2013 budget year.

Cobb County’s budget year begins Oct. 1, but county taxes are not collected until after the budget year has ended.

Tax assessors are now required to send assessment notices to all property owners by July 1. Hogsed said Cobb will be mailing notices for commercial properties by April 20, and residential notices around May 18.

Hogsed said he won’t know for about another month how many of those residential properties will see their values lowered. In the last two years, assessors have lowered the values on most — but not all — homes in Cobb.

“Some properties have not been lowered because they have continued to be undervalued as determined by comparable sales,” Hogsed said.

A state-mandated moratorium on increased valuations ended last year, and so a small percentage of Cobb’s homeowners will see higher assessments this year, he said.

Assessment notices will include an estimate of the taxes that will be due in the fall, but Hogsed stressed that it’s only an estimate, not a bill.

His office is making every effort to include city homestead exemptions in the tax estimate, Hogsed said, but the notices may not include exemptions filed close to the April 1 deadline.

“The key point here is that it is only an estimate,” he said.

Cobb’s gross tax digest has declined every year since 2008, when it was $33.82 billion. The gross digest encompasses all property, including vehicles, motor homes and utilities.

The gross digest first fell only 0.2 percent in 2009, to $33.75 billion.

The biggest drop came in 2010, when the gross digest fell almost 7 percent, to $31.42 billion.

Last year, the gross digest dropped 5 percent, to $29.71 billion.

In July, county commissioners narrowly approved a 16 percent hike in property taxes.