SAN DIEGO - As shoppers rush to take advantage of the post-Christmas megasales, county officials have issued a warning: Double-check receipts - especially on items with slashed prices.

Citing inspections at more than 1,000 stores throughout the year, county officials this month said that one out of three retailers surveyed had overcharged customers on at least one item.

Inspectors scanned 24,515 items in 1,035 retail stores and found that four out of 100 items were priced higher than advertised.

The results of the inspections, available on the county Department of Agriculture, Weights and Measures Web site, have prompted officials to urge shoppers to double-check receipts, especially on items with slashed prices.

The department is the agency that conducts the price verifications.

When discounted items were inspected, shoppers were five times as likely to be overcharged, in most cases because items marked down on shelves were not changed to reflect the lower price in the computers linked to the pricing scanners, department officials said this month.

Based on the inspections, county officials have estimated that shoppers are being overcharged by more than $100 million annually, adding that while scanners make it easier and faster to get through the checkout lanes, they can also lead to increased errors.

"During this busy time of year where people are spending extra money, it's easy to overlook pricing errors," especially when people are in a hurry, said Robert Atkins, who is in charge of the county's weights and measures department.

Most errors are inadvertent, and violators have been slapped with penalties ranging from $100 to $1,200, depending on the number of times overcharges occur and the number of items that are overpriced, county inspectors said last week.

But while most stores receive modest fines, the county has succeed in winning larger penalties in civil settlements for more severe violations.

Over the last two years, county prosecutors working with the district attorney's Consumer Fraud Unit filed civil suits against eight major retailers, including Albertsons, RadioShack Corp., The Sports Authority, Smart & Final, Toys 'R' Us, Baskin-Robbins, AutoZone and Longs Drug Stores. One of the largest civil settlements came in February, when RadioShack agreed to pay $569,763 in penalties and reimbursements, according to county records.

Secret shoppers

Scanner inspection programs aren't required by state law, and the county's program was adopted under the Consumer Confidence Protection Act, an ordinance enacted by the county Board of Supervisors in 1999.

During inspections this year, inspectors randomly selected between 25 and 50 items in 1,035 retail stores, depending on the number of scanners the store uses, and scanned the bar codes to compare the price that registered with the lowest advertised or posted price of the item.

County officials said that over the last two years, they have levied an estimated $85,000 in fines against nearly 250 businesses. That amount does not include large civil settlements.

In addition to paying fines, retailers found to have pricing errors are required to post a "Notice of Penalty for Failed Inspection" at store entrances for 10 days following any civil or criminal action taken by the district attorney's office, which is responsible for prosecuting violators.

More than 170 locations posted the penalty notices in the last two years, according to county officials. However, many of those retailers operate more than one store in the county, meaning that less than 170 individual retailers were cited.

In an effort to encourage shoppers to regulate retailers, the county ordinance also requires a "Notice to Consumer" urging customers to check their receipts and report overcharges to management or the county to be posted at all automated checkouts.

San Diego is one of 19 counties in the state that has a scanner inspection program.

Retailers who fail inspection

Retailers fail inspections for a variety of reasons, ranging from scanners that don't work properly to grocers not subtracting the weight of packaging from the price of foods sold in bulk. But more serious violations can result in prosecution.

In February, District Attorney Bonnie Dumanis announced a $569,763 settlement with the RadioShack Corp., saying that the multibillion-dollar corporation's "bad business practices" violated consumer trust and that it had engaged in "misleading" advertising during a four-year period at 698 stores throughout California. Forty-one stores are in San Diego County, she said.

RadioShack representatives didn't return calls for comment, but company officials were quick to cooperate with prosecutors to negotiate the settlement, according to reports from the district attorney's office.

The overcharges documented by officials in 282 inspections at 186 RadioShack stores averaged nearly $2 per item on about 650 items.

In addition to the $569,763 paid in penalties and reimbursements, RadioShack agreed to give customers any overcharged item that costs less than $3. On overcharged items that cost more than $3, RadioShack agreed to give the customer $3 off the lowest price advertised.

So far, RadioShack has complied with the settlement terms, which also included implementing a five-year program to correct inaccurate shelf and scanner prices, county officials said this week.

To view a list of businesses that have received overcharging violations, go to the County of San Diego's Web site.

To report a complaint to the county, call 1-888-TRUE SCAN or go to www.sdcawm.org.

- Contact staff writer Darryn Bennett at (760) 740-5420 or dmbennett@nctimes.com.