Police were called on Tuesday, 7 May after 27-year-old Mohammed Shah Subhani failed to return to his home in Hounslow, west London.
His family reported him as missing shortly before midnight, having seen him last at 12:30hrs that same day.
Officers are now calling for the wall of silence, which they believe to be surrounding his disappearance, to come to an end.
Mohammed’s white Audi Q3, registration LC67 CXS – an image of which was previously released by the Met – is also yet to be found.
“Mohammed, who is also known as Shah Khan, is incredibly close to his family and is only a few months away from becoming a father for the first time, so clearly his absence is having a devastating impact.
“The £20,000 Met reward is being offered for both information leading to the whereabouts of Mohammed, and also information leading to the identification, arrest and prosecution of anyone connected with his disappearance.
“Information suggests that Mohammed was in debt and attended the police station in the hope that he was to collect £4,800 from a matter that was not proceeded with. The money was not available – as it had been banked.
“He then went to an industrial premises on Derby Road, Hounslow where he met an associate who owed him £5,000. We believe that this money was paid.
Contact police, or Crimestoppers anonymously if you have information which can help to find him.
“Anything you share will be carefully assessed and acted upon where appropriate.”