You want to know the penalty under federal law for failing to report the theft or loss of a firearm.

Federal law requires a federal firearms licensee (gun dealer) to report any theft or loss of firearms from his inventory within 48 hours after he discovers it (18 USC § 923(g)(6)). A willful violation is punishable as a felony, which carries a fine of up to $ 250,000, imprisonment for up to five years, or both (18 USC § 924(a)(1)(D) and § 3571(b)(3)). A violation is willful if it can be established that the licensee understood the law’s requirements but knowingly failed to follow or was indifferent to them (T. T. Salvage Auction Co. Inc. v. Secretary, U. S. Dept. of Treasury, 859 F Supp 977 (E. D. N. C. 1994)).

The federal law does not apply to nondealers.