A man armed with a knife stole cash from a shop in Hedgerley earlier this week.
The robber went into the Spar in Hedgerley Hill at around 4.35pm on Tuesday and demanded money from the till.
Money was handed over to him and he fled the scene. No one was injured.
The man is described as being white, about 6ft tall, with a medium build. He was wearing a blue bobble hat, a black jacket, jeans and trainers and had a scarf covering his mouth.
Investigating officer, Detective Constable Jemma Tamplin, based at Aylesbury police station, said: "I am appealing for anyone who witnessed this incident to come forward.
"If you saw this offence take place, or saw a man matching this description in the area at the time, please get in touch."
If you can help with the investigation, call 101 quoting reference 43180008577.
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