Zotec Partners, a fast-growing physician-billing management company based in Carmel, has expanded operations by acquiring a family-owned medical-billing firm based in Florida.

Zotec said Thursday that it closed on its purchase of Medical Business Service Inc. on Sept. 7.

Medical Business Service, or MBS, is among the largest privately owned medical billing providers for hospital-based physicians, with clients concentrated in 10 states including Georgia, Florida, South Carolina and Tennessee. The company, which has 100 employees and is based in Coral Gables, declined to disclose its annual revenue.

In May 2010, MBS hired Zotec to provide technology services, including claims transmission and electronic data interchanges. The sale of the company was a natural outgrowth of that partnership, said Bing Herald, who served as president of MBS since he and a brother bought the 51-year-old company from their father in 1986.

“We felt as though we wanted to consolidate, to take advantage of scaling, eliminate overlap and overhead and be more price-competitive,” Herald said in a phone interview.  “We also wanted to feel like we have our own technology to bring value to clients.”

Herald declined to share details about the sale price or how many employees would lose their jobs because of the merger.

Zotec officials declined to answer questions about the deal Friday morning.

Zotec CEO Scott Law, who founded the company in 1998, said in a prepared statement that the acquisition is an extension of the “technology alliance” the companies formed last year.

“We are coming together to get better, not necessarily bigger,” Law said. “Right now, both companies are just focused on doing our jobs and continuing our attention on securing the financial performance of mutual clients throughout a seamless merger transition.”

The Herald brothers will lead the company’s client-services efforts but will not have ownership stakes in Zotec, Bing Herald said.

In 2009, Law told IBJ that Zotec was on pace to hit $65 million in revenue that year and aimed to hit $100 million in revenue by the end of 2011. As of 2009, the company’s 367 employees were based primarily in Indiana and California.