The Seattle Public Utilities agency fired three employees Friday and suspended a fourth for tampering with billing records.
The agency says an investigation found they waived late fees, readjusted payment periods or manipulated payment arrangements.
The employee action is the result of a review of billing data that began in April after the agency fired two other employees for crediting their own accounts.
Revenue losses are about $440. The agency says it's increasing controls of the billing system to prevent misconduct.
The agency provides water, sewer and trash disposal services in Seattle.