The trio claims Sean M. Larkin cost them dear when he failed to file state and federal income tax returns on their behalf between 2002 and 2009.
In court documents, obtained by the Los Angeles Times, a lawyer representing the three pop stars writes Larkin "falsely represented... on numerous occasions that he was taking care of everything and that they had nothing to worry about."
will.i.am, Taboo and apl.de.ap with fellow bandmate Fergie who employs her own business manager, and is not involved in the lawsuit.
The band members confronted Larkin after they discovered they had massive tax bills in 2009, and he assured them he would file the delinquent returns and cover all the costs. But, the suit alleges, "Larkin's representations proved to be false."
He was finally fired and the trio paid off its personal taxes, but Larkin allegedly has yet to provide them with financial records they need to complete returns for their touring company.
In a February deposition, Larkin acknowledged failing to file taxes for clients and said he "got in over my head with the amount of clients I had."