An offset mortgage basically uses the interest from your savings account against the interest charged on your mortgage. Usually your mortgage lender will link your mortgage and savings account into a single account, with the same financial institution. Each month, the amount you owe on your mortgage is reduced by the amount you have in your account, before working out the interest due on the mortgage. For example, if you had an offset mortgage of £100,000 and you had savings in your offset account of £25,000 you will only pay interest on £75,000. When your savings balance goes up, you pay less on your mortgage. If you continually keep your savings balance high, this could eventually result in your mortgage being paid of early. On the other hand, if your savings go down, you pay more on your mortgage. Your mortgage lender will plan with you the minimum amount you should leave in your account each month.