What is the best Internal Audit software for Company having 100 million USD annual turnover and can we get some demo for such internal audit software?

Unfortunately there is no good software available for IA which provides both documentation and analysis features. However different software can be used for each. For example for documentation of results and working paoers, IBM Lotus Notes is the best software. For Analysis ACL Analytics, Caseware Teammate are some of the very good tools.

It all depends on your requirement, turnover is not the only aspect to consider.