These are also be known as a high Loan to Value (LTV) fees, additional security fees, maximum advance premium or a high lending fee.

For example if a lender loans more than 75% of the value of a house, they run a greater risk of you getting into arrears. In order to cover this extra risk they might take out an insurance policy. The cost of this policy is passed onto you as a Mortgage Indemnity Guarantee. A lot of lenders will charge you this, however some may only charge if they are lending 80% or 90% of the purchase price. The final cost will be a percentage of the excess money they are lending, according to their own terms.