A “kick-back” occurs when the NFA Branch of the BATFE returns an application for a tax stamp approving the transfer of a federally regulated firearm. A cover letter is sent identifying one or more issues related to the documentation provided along with a Form 1 or Form 4 by a gun dealer or other party to the transaction.
You fix the problem and submit the corrected documentation along with a copy of the NFA Branch letter. Your application will be approved fairly quickly unless additional problems surface.