Elanga has completed a permanent move to Forest after making 55 appearances for Manchester United following graduating from their academy.
Nottingham Forest have agreed to pay a fee of £15m to take the Swede to the City Ground and managed to beat competition from Everton for his signature.
Manchester United could end up bagging as much as £20m from his departure but the add-ons are not easily achievable.
It has been claimed that the add-ons are heavily dependent on Forest qualifying for Europe while Elanga is at the club.
The Midlands club just about survived in the Premier League last season, finishing 16th in the league table.
They will hope to consolidate this term and have a better campaign but they are not being tipped to finish in European spots.
In fact, Nottingham Forest have not qualified for European football since 1995 and just got promoted to the Premier League last year.
It remains to be seen whether Elanga manages to play a big role in getting the two-time European champions back to continental football, which would end up benefiting his former club.
