If the total balance of all foreign accounts (including those the client had signatory authority on) amounted to $ 10,000 or more in the last year, you report on the Foreign Bank Account Reporting Form 114.  Go to the File menu when in your client's return, choose "Go to Foreign Bank Account Reporting Form 114". 

Any interest or dividends from these accounts gets reported like normal on the Schedule B.

If the balances in these overseas accounts (excluding those they had signatory authority on, I believe), amounted to $ 75,000 or more for a single person or $ 150,000 for a married couple (check the numbers on these at the IRS website, I am not 100% sure), this ALSO has to be reported on IRS Form 8938, which is filed with their tax return.  

Whatever you do, if you're filing corporate or partnership returns as well, and the entities have foreign subsidiaries or do business with related entities, then there's the Forms 5471 and 5472.  I avoid these types of clients like the plague and refer them out.  Those forms go on forever, are just too difficult to be worth most peoples' time and there are staggering fines if they are omitted or completed incorrectly.  NOT WORTH IT! Anybody who has to file those types of forms should go to a large local or regional accounting firm that has people on staff to deal with them.