The England international played second fiddle to David de Gea in the 2021-22 season and found his opportunities for game time extremely limited.
Henderson made three appearances in the Champions League, FA Cup and EFL Cup, as well as turning out on two occasions for the youth team in the Premier League 2.
However, the 25-year-old did not play a single minute in the top flight last term, and he is expected to leave in search of regular first-team football before the 2022 World Cup.
Newcastle United were strongly linked with a swoop for Henderson, but the Magpies are instead expected to sign Nick Pope from relegated Burnley.
Now, The Express reports that Henderson is now closing in on a loan switch to Nottingham Forest after a breakthrough in negotiations between the two clubs.
The report claims that Man United did not want an option to buy clause to be included in Henderson's loan contract, and Steve Cooper's side have agreed to that stipulation.
As a result, Henderson is expected to seal his temporary switch to the City Ground in the coming days, and United chiefs did not want to lose the goalkeeper permanently due to his wealth of admirers at the club.
Henderson starred for Sheffield United during a two-year loan spell between 2018 and 2020, and the 25-year-old has now made 29 appearances for Man United at senior level, keeping 13 clean sheets.
Henderson is set to arrive at the City Ground as current number one Brice Samba seeks a move away, with the 28-year-old not prepared to extend his deal beyond 2023.
Watford's Daniel Bachmann - who spent most of the season as Watford's number two behind ex-Man United goalkeeper Ben Foster - is thought to be one of the names on the Red Devils' goalkeeping wishlist.