While a 100% schedular rating is based solely on the severity of your disabilities, TDIU considers how those disabilities impact your ability to work. With TDIU, you can receive compensation at the 100% level even if your actual disability rating is lower. While you may be able to work with a 100% schedular rating, if you are receiving TDIU, it means you are not capable of maintaining substantially gainful employment. If that changes, and you become able to work, VA may sever entitlement to TDIU.