I have been using MTBC for 2 years for 4% of collections and I am very satisfied with quality of their work. Collections are good.T hey are very polite and responsive to corrections. Of course, sometimes they do small mistakes like missing modifiers, which I monitor and correct promptly. I look over all my EOBs and assign my receptionist or MTBC to investigate denials. I would spend much more money hiring an in-house billing person and paying for billing software and postage expences. I believe "AC "partnered" vendors make it possible to upload bills directly from AC to the billing company, otherwise we would have to printout daily superbills and scan them for FTP upload.
