No problem.
A form 1 is an application to make a silencer, short barrel rifle or shotgun. Basically extortion money where you give them $200 tax for a permission slip to saw off the end of your barrel.
A form 4 is a transfer of an already existing silencer, short barrel rifle, shotgun, to you. Basically extortion money where you give them $200 tax for a permission slip to have a gun with a shortened barrel, etc.
There is probably a better "legal answer", but, my answer is just as correct as the legal one. The form 1 and 4 are the forms you fill out and pay the $200 to have the item in the first place.