There is no law saying private individuals must maintain records of gun sales.
Correct ... BUT it is a good idea to keep records since lawsuits can crop up. I sell from my private collection occasionally and I have taken to getting a driver’s license number to keep alongside the serial number of the ‘tool’ sold. BTW, I have a nice Rockola Carbine I would let go of, for the right price.
True, but it’s not a bad idea. If a gun I once owned was used in a crime & traced back to me, I would produce the receipt, “Nope, sold that one years ago, check it out.”