Ten things that you need to know about...

1. These accounts pay a fixed rate of interest over a defined period. The interest paid on the account will therefore not be affected by changes in interest rates during that period.

2. Interest is normally paid net of income tax at 20 per cent.

3. If you are a non-taxpayer, fill in form R85 at the time of applying for the account, so your interest is paid gross.

4. Some accounts only allow a one-off lump sum to be deposited.

5. At the end of the term, make sure you instruct the bank or building society as to what to do with your money. Susan Hannums of independent adviser AWD Chase de Vere warns that if a provider doesn't hear from you, it may roll your money into a follow-on bond at a less competitive rate.

6. Aim to earn about 5 per cent gross on your money at the moment. Birmingham Midshires (0845 603 2286) is paying this on deposits from £1 for a year, while Anglo Irish Bank (0845 455 2222) is paying 5 per cent gross on £500 or more for two years.

7. Don't tie up your money for longer than three years. Hannums points out that providers are currently paying 5 per cent regardless of the length of the fixed terms, indicating they can't predict what is going to happen. She recommends keeping your options open over the longer term.

8. Check current rates at www.moneyextra.com or www.moneyfacts.co.uk

9. If it's not vital for you to earn a fixed rate, do check out instant access internet accounts which may pay more. Alliance and Leicester's Online Saver Issue 2 www.alliance-leicester.co.uk pays 5.15 per cent gross, including an initial bonus rate of 0.9 per cent until March 31 next year.

10. Early access to your money in these accounts is usually only possible on closure of the entire account, and is likely to be subject to a large penalty.