Great question, Yes the IRS will and is tracking bitcoin profits.They have already been in contact with coinbase and other exchanges to get a list of people who move just money.Irs will get there money this is why binance is shutting down in USA. If you think they want to they dont but USA Can do things if they dont feel your replying the info the USa wants.they dont want to de a target..I'm sure they dont care about losses but gain are taxable . As of now 10 kor 15k letters have gone out. It's better tg o show you gains and take off losses now the wait 10 years.If you made money you may loss everything in penalty not reporting.but not giving tax advice.