Simple past tense and past participle of overbill.(verb)
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Use "overbilled" in a sentence
"State auditors are investigating whether Visiting Nurse Service of New York, a $1 billion home-care company, overbilled the Medicaid program."
"In the health-care video, students in green polo shirts and khakis dance through the school's hallways - one wears medical scrubs and has a stethoscope around her neck - and sing lines that include, "Politicians in conflict, there are too many people who are sick" and "I've seen people ill, patients overbilled, people uninsured in poverty, that's for real.""
"The city's rent-control law, which dates back to 1987, when white urban homesteaders began moving there in large numbers, allows tenants who believe they've been overbilled to petition for a reduction."