It happened shortly before 10.50pm last night (Thursday, February 18) at the One Stop Store in Marsh View Court.
Two men entered the shop and threatening a male member of staff with what was believed to be a hand gun. They demanded money from the till and then left with a three figure sum of cash.
The store worker was not injured but was left shaken after the incident.
The suspects both described as men of around 5ft 9ins tall and wearing dark clothing, scarves and white gardening gloves, left the scene.
Enquiries are continuing today. Anyone with any information is asked to contact Essex Police on 101 or Crimestoppers anonymously on 0800 555 111.