B. G exit fees

Hey guys, Just transferred over from British Gas. I’ve been charged exit fees, but at the moment, have no bill showing them. I have searched to no avail regards the following, so wondering if anybody knew, IS THERE A TIME LIMIT ON PROVIDING EVIDENCE OF EXIT FEES?
Thanks in Advance

Not aware but should be ok if final bill is dated, it can take 6 weeks to get your final BG bill which you then send to Bulb. (I think email a copy)