Which of the following forms is filed not with the IRS, but with the Financial Crimes Enforcement Network (FinCEN)?

The correct answer is D, which refers to the Foreign Bank Account Report (FBAR). This form is required to be filed with the Financial Crimes Enforcement Network (FinCEN) rather than the IRS. The purpose of the FBAR is to report financial interests in foreign bank accounts, securities accounts, or other financial accounts where the aggregate value exceeds $10,000 at any time during the calendar year.

FBAR is part of the U.S. government's efforts to combat money laundering and to ensure that U.S. taxpayers report their foreign financial accounts and pay taxes on income earned from those accounts. It is important that individuals meet the FBAR filing requirement as failure to do so can lead to severe penalties.

The other forms mentioned serve different purposes and are filed directly with the IRS. Form 8938 is used to report specified foreign financial assets and is part of the requirements under FATCA (Foreign Account Tax Compliance Act). Form 8865 deals with information regarding a controlled foreign partnership, and Form 3520 is related to reporting transactions with foreign trusts and the receipt of certain foreign gifts. These forms are integral to reporting foreign financial interests to the IRS but do not involve FinCEN.