If you were sent a tax return in April 2008, it will be based on your income and allowances for 2007–08. Many older people who fill in a self-assessment form are now sent a Short Tax Return. It is simpler to complete – though it comes with a 24 page guide – and does not help you work out the tax due. Whichever form you get, you should complete it by 31 October 2008 or you may face a £100 fine. However, the fine can never exceed the amount of tax you owe, so if you in fact owe nothing you will not be fined. You can avoid the fine by filling in your tax return online as long as you do that by 31 January 2009.

If you do get your return in by 31 October the Revenue will work out the tax you owe. That has to be paid by 31 January 2009. If the payment is late you will have to pay interest on it and if you delay beyond the end of February 2009 there will be a surcharge as well - of 5% of the tax you owe. There are further penalties if you delay longer.

You must keep any documents relating to your income for at least one year after the tax on it was due on 31 January. But if you are self-employed the time limit is five years. So on 1 February 2009 you can normally destroy documents relating to the tax year 2006–07 or 2002–03 if you are self-employed. If there is an enquiry into your financial situation you must not destroy any documents until it is over. You must also tell the tax office if your income changes significantly during the tax year.

Contact your local HM Revenue & Customs Enquiry Centre for more advice. You can also get advice on self assessment in the evenings or at weekends by calling the HM Revenue & Customs Self Assessment Helpline on 0845 9000 444.

Most pensioners are not affected by self assessment, so don't worry if you aren't sent a tax return. But if you are sent one you must complete and return it by 31 October 2008 – or complete it online by 31 January 2009 – or you may be liable to a penalty of up to £100.