A Form 3520 is filed separately from your tax return.
The 3520 is most often filed when you receive a gift from a foreign person in the amount over $100,000.
IRS Form 3520 - https://www.irs.gov/pub/irs-pdf/f3520.pdf
IRS Form 3520 instructions - https://www.irs.gov/pub/irs-pdf/i3520.pdf
