A form guide to calm the nerves

Have you completed your tax return for the year to April 2000? The Inland Revenue says that over 3m forms are still outstanding, and threatens a £100 fine if you don't file by the end of this month.

Tax returns are issued to just over 9m people - or one-third of all taxpayers - typically those who are self-employed, company directors and higher paid employees, and other people with untaxed income such as rents from property.

If your return is still in its pristine blue wrapper, you had better open it, gather your financial records, and get to work. If you need help in wading through the form, you may phone your tax office, or the Revenue's helpline at evenings and weekends (0845 9000 444). And as you may also need to ask for extra pages - see page 2 of the form - you should not delay.

Some people put off filing because they do not have all the information needed. If you are unsure of the income received from your bank or building society, you may ask them for a certificate of interest paid to you. They must provide this free of charge.

If you had a salary or occupational pension, income and tax details should be on your P60 or P45, with taxable benefits-in-kind reported on form P11D. If you have mislaid these, your employer or pension administrator should hold the relevant details (although they will not normally offer duplicate certificates). If they won't offer you the information you need for your return, it may help to know that they should have reported it directly to the Revenue last summer and your tax office may agree to give it to you.

Sometimes it is impossible to obtain exact figures before the deadline. For example you may not have kept records of some trading income or expenses, or you may be awaiting details of income from a trust or deceased estate which has not completed its accounts. The Revenue says you should not allow such difficulties to delay the return and that you should use an 'estimate' or 'provisional figure', explained on page 27 of the Tax Return Guide.

The most important distinction between these two terms is that if you enter a provisional figure you will need to submit further information within a specified period.

If your form was issued to you on or before October 31, 2000 you must file by January 31. Normally you should post it to your own tax office but, if you are running late, you could take it by hand to any local office. Defaulters are threatened with a £100 fine but, due to a flaw in the legislation, no charge can be made if the form is received by the Revenue on February 1, or found in a tax office letter box at 7am on the following morning. If the form was issued after 1 November, you may file up to 3 months after the date of issue shown on the front page.

Whatever date you send it, it is vital that you take a photocopy of the return. This provides some evidence that you have filed, and will also help you to check the Revenue's figures.

Although self assessment was introduced four years ago, there is still confusion over the obligation to calculate your tax. The Revenue promised to do this in good time if you filed by September 30, giving the impression that people filing now must calculate their tax for themselves. This is not true; the taxman will do the sums whenever you send in the form, although it may take a few months. So if you believe that you still owe some tax for 1999/2000, which will fall due on January 31, you may want to make an estimated payment this month to avoid interest (as well as the 5 percent surcharge added to tax paid after 28 February).

While most taxpayers keep their affairs up to date, a minority are in serious arrears. About 10% of self assessment taxpayers have not yet filed their tax returns for 1998/99 and earlier years. When a return is long overdue, the taxman may make a 'determination' (ie estimate) of your tax for the year concerned, and take action for payment through the courts. There is no right of appeal, although the determination is withdrawn as soon as the return is filed.

• David Brodie is director of TaxAid, the charity which provides free tax advice to people who cannot afford professional fees. Phone 020 7624 3768 between 10 am and 12 noon, Mondays to Thursdays. More information is available on TaxAid.