That will be because he will have been found to be fraudulent in the eyes of HMRC - nothing to do with his lack of records beyond year 5.
But if you don’t keep them past 5 years then you cannot defend yourself or prove your innocence if you get an investigation as you wouldn’t have any paperwork , legally you have to keep it 5 years for your own piece of mind it’s worth keeping the much longer
You'd only get an investigation where they pore over records that far back if you had other reasons to be on the radar.
I know a chap who got done for £20,000 when it was seven years. They only went back that far.
If they had found his Caribbean island claimed as a garden office they aren't going to worry about whether the £10 spent on petrol for his wife's car was a business expense or not in 2006.
