501 C.M.R. 19.05
All transactions involving a firearm within the commonwealth, including, but not limited to, all purchases, sales, rentals, leases, loans or other transfers shall be reported by all parties to the transaction via the MIRCS portal within seven days of the sale, rental, lease, loan or other transfer. No report shall be required for a loan of a firearm to a duly licensed or exempted person for a period of less than seven days.