If you want to avoid a £100 fine, file your tax form now

Taxpayers are set to fork out an estimated £100m in fines this year for returning their self-assessment returns late, according to research by Independent Financial Advice Promotion. With less than two weeks till the 31 January deadline, anyone who has yet to complete their forms must now file them online and as soon as possible if they want to avoid an automatic £100 fine.

If you have not filed online before, you will need to register at the HMRC website and wait for a pin code enabling you to log on. It can take up to seven working days to receive the code, so in practical terms you will need to apply by 21 January.

"Those who have chosen to bury their heads in the sand need to go online, sort out their pin codes and get on with it", says Chas Roy-Chowdhury, head of taxation at the Association of Chartered Certified Accountants. The forms have also had a facelift since last year, with various boxes being merged, removed or added, so it may take some people longer than they expect. But there is plenty of free help at hand on the HM Revenue and Customs (www.hmrc.gov. uk) and Direct Gov (www.direct. gov.uk) websites.

With the credit crunch taking its toll, it is important you are aware of any tax-deductible expenses. If you're self-employed, you can claim tax back for various running costs that are necessary to your business, such as stationery, repairs and uniforms. On top of these running costs, you can get tax relief on assets needed for your work, such as machinery and computers – known as capital allowances.

If you use a car for business purposes, you cannot claim for your normal commute to and from your place of work.

You may, however, be entitled to allowance relief for other business travel. This is calculated by multiplying your business mileage by the approved mileage rate, which for cars and vans is currently 40p for the first 10,000 miles and 25p per mile thereafter.

If you work from home, you can also claim for a percentage of your electricity and heating bills, broadband bills and phone bills. But don't be tempted into making unreasonable claims.