These companies sell a service rather than a product. They act as your billing department, and sometimes also as your QA department. Send your patient and visit data to them, either on paper or (usually) electronically and they enter it into their own software, have experienced clinicians check it over, and submit OASIS files, RAPs and claims for you. Sometimes such a company gives you the option of purchasing their software and controlling your own billing or contracting it out to them. Other companies sell no software at all and offer the outsourcing service exclusively. .