I need to file form 3520 this year. I have filed extension for my tax return. Do I have to file additional extension for the 3520? Thank you.

If a U.S. person is granted an extension of time to file an income tax return, the due date for filing Form 3520 is the 15th day of the 10th month following the end of the U.S. person’s tax year. 

Send Form 3520 to the: 

Internal Revenue Service Center

P.O. Box 409101

Ogden, UT 84409. 

Form 3520 must have all required attachments to be considered complete

Instructions for Form 3520: https://www.irs.gov/pub/irs-pdf/i3520.pdf