The Chatham County Assessor's Office placed an IKEA furniture distribution center in the unincorporated county, but it put the center's contents in the City of Port Wentworth, according to a tax officer.
That led to a huge budget shortfall for the city, and Port Wentworth slashed its budget after the error was discovered.
Interim Chief Appraiser Maryellen Burner discussed the discrepancy Tuesday as she was questioned about what led to the error.
The city was faced with having to repay more than $400,000 in taxes because of the mistake.
Burner said a new computer program led to last summer's discovery that an employee had incorrectly placed the inventory in the city when it went on the tax roll in 2008. Burner said they could have done nothing to detect the mistake earlier.