The police have handed files to the Crown Prosecution Services about the 'proxy' donations from David Abrahams.
It will now be decided if there is enough evidence to prosecute.
The donations, which totalled £664,000, were given to the Labour party by Mr Abrahams, a property developer, through various other individuals.
He says he had no idea he was doing anything wrong.
The affair led to the resignation of the party's general secretary, Peter Watt.
Gordon Brown promised to return the money and denied any knowledge of the donations.