Officers are appealing for information after Doffs Supermarket on Chorley Old Road in Smithills was robbed on Wednesday 6 February 2019.
Around 9.30pm, a man – armed with a knife and a metal bar – entered the store and threatened members of staff whilst demanding cash from the till.
Thankfully no-one was injured during the robbery, but staff members were left understandably shaken.
The offender fled on foot with the stolen cash and is described as a white man, of slim build, and around 5ft 8ins tall. He was wearing a black balaclava at the time of the robbery.
Anyone who has any information about the robbery should call police on 0161 856 5757 quoting incident number 2138 of 06/02/19.
Details can also be passed on anonymously to the independent charity Crimestoppers on 0800 555 111.