Hinkley was last seen at his home on Madras St in Edgeware on Christmas Day 2015.
He spoke to a family member about 7.30am that day and has not been seen or heard from since.
His body was never found and his disappearance was out of character, leading police to "fear the circumstances of his disappearance are suspicious", Detective Inspector Scott Anderson said.
"Police have made extensive enquiries into the disappearance of Richard Hinkley but have been unable to provide his family with any definitive answer to what happened to him,” said Anderson.
"We have to keep an open mind, however, it is extremely odd that Richard has just disappeared.
"He has not made contact with anyone in the past six years, his bank accounts haven’t been touched.
"Someone out there either recognises this man or knows where he is, and our aim is to give his family the closure they deserve after such a long time."
Anderson said the reward will be paid for information or evidence which "leads to Hinkley’s location and/or the identity of any person or persons responsible for his disappearance".
The reward offer will remain in place until January 31, 2023. Anyone with information should call police on 105 and quote 160210/8867, or phone Crime Stoppers anonymously - 0800 555 111.
