Laundering money is a dirty business.

Consider the case of the First National Bank and Trust Co. of Kearny, N.J., which pleaded guilty yesterday in U.S. District Court in Newark to 75 counts of failing to file currency transaction reports. The maximum fine for each count is $1,000. Its assistant vice president, Robert Comer, also pleaded guilty to the same charge and faces a maximum penalty of a year in prison plus a $1,000 fine.

The Internal Revenue Service requires banks to report cash transactions of $10,000 or more. Large amounts of cash changing hands often tip the IRS off to tax evasion and law enforcement authorities to illegal activities. Money then is "laundered," or made "respectable," by transforming cash into cashier's checks or some other type of bank paper and depositing it elsewhere.

Examinations revealed that the First National Bank and Trust Co. had filed currency reports with fictitious names between July 1980 and January 1982. The cash deposits were traced to John C. Bilotti, also known as W.L. Jackson and John Lindi. Bilotti, whom an IRS spokesman described as a "middle man for organized crime," was subpoenaed by a grand jury. The day before he was to appear, Bilotti disappeared.

He turned up on Oct. 24 two blocks away from the IRS building in Manhattan, in the trunk of a car, dead.