Hey, I have a investment account in Brazil and wondering if I have to: 1) Declare its existence (FBAR) 2) Declare the amount of dividend/interests I got 3) How to tax it

[DaveF1006]

Yes, there is a FBAR requirement to report this if the account balance exceeds $10,000 in a calendar year. You would report this here. 

Also, you may have a FATCA (8938) reporting requirement to report if the value of the account $50,000 on the last day of the year or exceeds $75,000 at any time during the year if you are single. Those values double is you file married Filing jointly.

The only time you need to worry about being taxed is when distributions are made to you either by a interest payment, dividend payment or stock sales. The IRS or Treasury Dept  is not interested in taxing your account based on it's existence.  it is only concerned if distributions are made.

The FBAR and 8938 are only informational forms that the IRS requires but filing them will not require the payment of taxes. There are stiff penalties though for not filing these when required.