I have a joint account with my parents who are foreign person. In 2016, they received foreign gifts for over $100k to the joint account. Do I need to report form 3520?

That's a good question you ask.  The answer to it is that that if your name appears on the account as a joint owner, and you are a United States taxpayer (either a citizen or resident alien), and the total amount of the foreign gifts received exceeds $100,000, then you are required to file Form 3520.

While the TurboTax program does not contain Form 3520 among its many tax forms, fortunately Form 3520 can be completed manually, outside of the software, and then filed (by mail) separately from the rest of your tax return.

Complying with Form 3520 shouldn't be too difficult either, as there is never any tax directly due when filing it.  All it really costs, then, is a stamp and the time necessary to complete the form.  Fortunately, despite being 6 pages long, it's a relatively easy disclosure, as far as such IRS tax forms are concerned.

For reference, here are some courtesy links to Form 3520 and its instructions:

https://www.irs.gov/pub/irs-pdf/f3520.pdf

https://www.irs.gov/pub/irs-pdf/i3520.pdf

In addition, given the existence of your joint account, there are two separate financial disclosure forms that may be required (beyond Form 3520); each also has different reporting rules.

One is known as IRS Form 8938, and can be attached to the relevant yearly Form 1040 tax return.  The other is FinCen Form 114, which can only be filed via the internet.  The following Internal Revenue Service webpage describes them in some detail, and provides their dollar value reporting levels:

https://www.irs.gov/businesses/comparison-of-form-8938-and-fbar-requirements

 

If you are not already familiar with these foreign financial account disclosure rules (which apply to US citizens, as well as resident aliens), then you are respectfully encouraged to learn more about them, as the US Internal Revenue Service has become increasingly vigilant in enforcing these offshore financial account rules in recent years.

You can read more about IRS Form 8938 and FinCen Form 114 through the above link.

Thank you for asking this important question.