This paper describes successful implementation of a Rule Based System at MTBC, for applying billing compliance rules on medical claims. Rule engine has been developed in Structured Query Language as stored procedures, which is one of the unique features of this rule based system. Implementing rule engine in SQL has provided two major benefits. Firstly, as operational data of the organization is in relational form, stored in Microsoft SQL Server database, therefore rule engine, using the native language, works at real time without any need of data transformation for working memory. Secondly due to SQL server, rule engine is using interpreted approach instead of compiled approach, which helps dynamic updating, editing and execution of rules. A rule is represented as a query stored in database, along with associated attributes like rule name, rule description and rule priority. 'where' clause of query contains condition and then part of the rule. A rule editor has been developed to facilitate domain users to edit rules in English like format, which is then translated to SQL statements. Editing of business logic has become very easy in MTBC billing software by using MTBC-RBS.