It is always a good idea to work out roughly how much tax you think you owe even if you leave it to the taxman to do the full calculation. That way, you shouldn't get any nasty surprises, and if there is a big difference between your rough estimate and the taxman's bill, it may well be due to a mistake on the Revenue's part. The Revenue's own figures show it miscalculates the tax due in 28% of cases.
It is not just the Revenue that makes mistakes. Thousands of tax returns are rejected or corrected by the Revenue every year because of simple mistakes made by people when completing their form.
Here are 10 of the most common errors to avoid:
1. Failing to fill in all the relevant sections and pages. Go through the form carefully after completing it to make sure you have not missed anything. The same applies to any supplementary pages you have asked for.
2. Ticking the boxes on page 2 to indicate you have all the supplementary pages you need, then not including them when you return your form.
3. Failing to fill in separate supplementary pages for each employment, if you have more than one.
4. Stating that information may be found elsewhere, for example, 'per P60', rather than entering the figures on the form, or sending information in a covering letter or attached accounts.
5. Stating that a figure is provisional when it is actually an estimate. (If a figure is provisional, the Revenue will expect you to come back with a more reliable figure later.) You can give an estimate if you really don't have the exact figures, but explain what you have done in the white space at the end of the form.
6. Entering the list price of a company car in box 1.16 instead of the actual benefit.
7. Entering the net figure for personal pension contributions paid by an employee, instead of the gross amount before tax relief given at source. Higher rate taxpayers that do this will lose out on some of the tax relief they are due.
8. Reporting the capital balance on a savings account rather than the interest earned in the year.
9. Providing answers that don't add up in Q10 on interest and dividends. You have to state the net amount (cash received after tax), the tax deducted and the gross amount (before tax). The net amount plus tax deducted should add up to the gross amount.
10. Failing to tick 'yes' at Q19, asking the Revenue to refund any overpayment of tax. In such cases the Revenue will hold any repayment against future tax liabilities.
Finally, remember to sign and date your form - failing to do so is one of the most common mistakes of all. And take a photocopy - it's useful for future reference and in case the Revenue mislays the original.
If you need more help and information on how to complete your tax return call the Helpline on 0845 9000 444 (open evenings and weekends - calls are charged at local rates) or visit the Inland Revenue's Self Assessment web site
