Provide a fixed and guaranteed rate of interest, which is added to investment and paid tax-free at the end of the term (two or five years).

There is a maximum investment of £10,000 (minimum £100), although there is no limit when reinvesting maturing certificates in a later issue.

New "issues" of certificates are made each time interest rates change. If they are cashed within their first year, interest is not normally payable. Between the end of the first year and maturity, the interest payable on early encashment will be reduced, but still tax-free. Interest is credited every three months.