About 4.15pm on Sunday, February 7, a man withdrew money from an ATM at a shopping centre on Ranford Road in Canning Vale.
The man took his card from the ATM but he forgot to take the cash and walked away.
A short time later, the cash was removed from the ATM.
Police have released a CCTV image of a man and woman who they believe can assist them with their inquiries.
The woman is described as being light skinned, 25-35 years old, of thin build and having shoulder length dark hair.
She was wearing a black sleeveless top and a lightcoloured dress.
The man is described as being light skinned, 25-35 years old with a thin /medium build and short, dark hair.
He was wearing a light blue polo shirt and light coloured shorts.
If you know the identity of these people or have any information about the offence, call Crime Stoppers on 1800 333 000, where all calls are strictly confidential, and rewards are offered.
Quote reference number 8032.