Again, a quote from Alistair Johnstone, who I presume you're about to dismiss as a muck raker
“On the assumption he is being open with the fans, he has borrowed £24 million, he paid £18 million to buy off the debt, so the club should be £42 million in debt."
The Telegraph
As for the 2.8M bill ..
http://www.dailyrecord.co.uk/news/scottish-news/2011/09/02/taxman-issues-rangers-with-final-warning-over-s2-8m-tax-bill-86908-23390085/