hi,

see it is quite difficult to study the both of the course simultaneously. however Master of Commerce is a postgraduate master's degree focusing on commerce-, accounting-, management- and economics-related subjects : where Tax law or revenue law is an area of legal study in which public or sanctioned authorities, such as federal, state and municipal governments  body of rules and procedures to assess and collect taxes in a legal context are Included. so this two course is seem to different , so you must decide which of the area you have keen interest AFTER COMPLETING M.COM YOU MAY DO WORK AS A FINANCIAL ASSISTANT, BUSINESS ANALYST, ACCOUNTANT ETC.