A member of the public reported that a male visited a house in the Morley area of Leeds stating he had just come out of prison and was selling goods, before asking to be allowed into the property.
The occupant refused him entry and the items he claimed to have for sale were never seen.
West Yorkshire Police also said the man had a document in his hand which could have been some form of identification, but that was not confirmed.
The force are now warning other residents that this practice is not part of the official rehabilitation programme.
A spokesperson for West Yorkshire Police said: "A report has been received from a member of the public that a male has attended at an address in Morley stating he had just come out of prison and was selling goods, the male asked to come into the property but was refused by the occupant.
"The male in question had a document in his hand and this may have been some form of I.D but this has not been confirmed, the items he was claiming to sell were not seen by the occupant.
"We can confirm that this practice takes place countrywide but it is not part of any official rehabilitation programme.
"Some doorstep sellers may say it has been set up by the Probabtion Service and some may say it is for charity purposes.
"If you have any concerns or this happens to you, please contact 101 or complete the online reporting form on the main WYP website."
For the latest crime news from around Leeds - join our dedicated Facebook group by clicking here.