Andy,
Whilst I appreciate your concerns about a fellow colleague, this is how hearsay and nasty rumours can start.
Thankfully, being an active member on the forums, I can answer this.
I know who you're speaking about and I am dealing with this person's "investigation" myself. I hope you have told him that you have posted this, not only about him but about us as well?
HMRC are quite at liberty to pull anyone's file and take a good hard look at it. If you look back over other threads, you'll see we have answered this kind of query before.
It may also be worth noting that this claim is for over 4 years worth of tax rebate, which is why it's a high figure. It's also worth noting that the refund hasn't been paid out yet, so we have not been paid either, but despite that, we are still doing what we can to assist in what HMRC need. Also, because it's not been paid out, it doesn't get clawed back either.
And, I'm not sure I like the implication you're making that it could be Bettertax's fault. And that's me "just saying".
This is not money owed in tax, by the way.