Two former top officials with the New York Racing Association , Vince Hogan and Clement Imperato, pleaded guilty Thursday to tax evasion charges in federal court on Long Island. Hogan and Imperato, ex-directors of the parimutuel department of the NYRA, admitted they conspired with other NYRA employees to defraud the Internal Revenue Service. The guilty pleas came out of a long-running investigation of NYRA that led to tax evasion charges against two dozen parimutuel employees. To date, 23 of the 24 defendants have pleaded guilty. Hogan and Imperato both acknowledged letting parimutuel clerks take money from their registers at Belmont, Aqueduct and Saratoga racetracks. The clerks then claimed their drawers were short money because of mistaken overpayments to bettors. The clerks would keep the cash, and the overpayment was deducted from their paychecks. But no taxes were taken out of the deducted money, basically giving the clerks a tax-free bonus. Neither Hogan nor Imperato had any comment as they left the courthouse. The pair's role in the scam was signing off on the forms filled out by the clerks about their registers. The defendants, who had no previous record, each face up to five years in prison and a $250,000 fine at their Sept. 10 sentencing. Federal guidelines suggest they would likely receive 10 to 15 months behind bars.