Mortgage lenders are burying fees in the small print of mortgage documents and are rarely detailed on lenders' websites. Here are six to watch out for.

GOING FROM INTEREST-ONLY TO REPAYMENT TERMS, OR VICE VERSA This used to be free but most lenders now charge for 'administrative work'. Lloyds TSB and Cheltenham & Gloucester charge £77, Abbey and Northern Rock charge £75 and many other lenders charge between £50 and £75.

Some even charge for an illustration of what your new payments will be (Lloyds TSB has a £106 fee for a 'hypothetical account illustration'). To avoid this, work out the figure yourself at

CHANGING YOUR MORTGAGE TERM If you can afford to pay a little earlier and reset your term from 25 years to 21, your total repayments fall dramatically. Five years ago this tended to be free - now it costs. Co-operative Bank charges £54 to alter a term while building societies such as Skipton charge £50.

NEEDING SOME EXTRA PAPERWORK Abbey now charges £25 for duplicate statements and £35 for retrieving and copying documents. Most other lenders charge at least £15 for the service, though some will give you account access online so you can print out anything you've lost for free.

LETTING OUT YOUR HOME Most banks now make money out of 'accidental landlords' and charge 'consent to let' fees as well as increasing interest rates if you move out and take in tenants. Skipton building society has one of the lowest tariffs - its consent fee is £100 - and it increases rates between 0.5 and one per cent depending on the size of your loan and the value of your home. Many lenders have fees three times higher with similar rate increases.

CHANGING YOUR HOME INSURANCE Lenders love selling their own-label insurance - but it's often a third more expensive than cover available on the open market. If you buy a policy independently many lenders charge £25. Fortunately, providers such as Barclays, NatWest and Tesco offer £25 bonus payments to new insurance customers.

GOING INTO ARREARS The Financial Services Authority is investigating how lenders hit borrowers with extra fees when they fall behind on mortgages. But until it reports, penalties will continue. Costs start at £10 for the first letters about arrears (C&G) and £30 for unpaid direct debits (Northern Rock) to £100 fees for instructing external debt counsellors (Halifax) and £40-a-month penalties for borrowers in arrears (Barclays). Many lenders also add several hundred pounds to borrowers' bills once repossession procedures begin.