how can I complaint about black money

U can post a letter about it to the Income Tax Department regarding the same and u can state that ur identity shouldn't be revealed for this...

The Tax Authorities will do their work without any disturbance to u...

They'll scrutinise such person and find all the fraudulent activities of him...do it asap...as every citizen is responsible for paying tax and also making others paying tax and should not cheer others to evade..