US HB4220

Requires FinCEN to request information from financial institutions within 1 year about how homegrown violent extremists and domestic terrorism perpetrators procure firearms and accessories for lone wolf attacks

FinCEN must issue an advisory on identifying and reporting suspicious financial activity related to terrorist firearm procurement within 540 days if sufficient information is collected

FinCEN must consult with the FBI Director, ATF Director, and firearms sellers before requesting information, and must tailor requests based on financial institution size

If insufficient information is collected, FinCEN must report to Congress explaining the methodology used, barriers encountered, and why the advisory could not be developed

FinCEN must promulgate rules within 90 days defining "firearm accessory," "homegrown violent extremist," "lone wolf," and "lone actor" in consultation with FBI and ATF