And Ferdinand, who played with Ronaldo at United for six seasons, hopes his former club can finalise a deal for the four-time Ballon d'Or victor.
The Real Madrid supremo also assured fans that Ronaldo would honour his contract with the La Liga champions.
The guilty pleas of Di Maria, Mascherano and Messi, however, would suggest this is not always the case and Mourinho and Ronaldo will need to be certain the offshore companies they set up to receive their image-rights payments are entirely legitimate.
Ronaldo's agency, Gestifute' released a statement last week regarding the allegations, saying "it is clear that the football player did not try to evade taxes".
It comes a day after former boss Jose Mourinho was also accused of tax evasion by Spanish prosecutors.
Ronaldo is now on worldwide duty with Portugal at the Confederations Cup and was named man of the match after heading home his side's winning goal against the hosts Russian Federation.
The agency published copies of the certificates.
As Real Madrid coach from 2011 to 2012, the Portuguese coach is alleged to have not declared income from image rights deals to obtain an "illicit benefit", according to Spanish prosecutors.
A source confirmed to ESPN FC that Ronaldo wants to leave Real Madrid this summer, following the accusations.
The complicated structure used by Mr Mourinho also incorporated two Dublin-registered companies registered to the north inner city address of Moore Stephens accountants.