Dunnes Stores has been fined €1,500 and their premises on West Street in Drogheda has been ordered to close for four days after the company was convicted of selling drinks to an underage person.
The company had pleaded not guilty at Drogheda District Court to a charge of selling alcohol to a person under the age of 18 on 19 December, 2011.
A 15-year-old girl, who was on work experience in Drogheda Garda Station, agreed to be a test purchaser carrying out the operation.
She told the court she bought four bottles of Smirnoff Ice but was never asked for identification.
Garda Sgt Donal McGivern said he was behind the girl when she purchased the alcohol.
The duty manager was beside the assistant but did not stop the sale going through, he said.
It is the first conviction of this type for the company.