After that there can be further penalties just for not filing the form regardless of any tax that may be due.
If this is the first time you have had to do it start now – there are steps to take before you can file online.
There are more than 100,000 people who get child benefit and they or their partner has an income above £50,000 who have not yet filed online which they must do to pay the tax.
You will also have to fill in a self-assessment form if you are self-employed (even if you are also an employee and do a bit of self-employment on the side), a minister of religion (of any faith), a company director, have an income of more than £100,000 in the tax year, have income from savings or investments of more than £10,000 (or £2,500 if it is untaxed income), have an income of more than £2,500 from property (but not under the rent a room scheme which is tax-free up to £4,250 a year).
Read more about the things you have to pay tax on.
There are other circumstances in which you need to fill in a return. And if HMRC has sent you a form or told you by email or letter to file online then you must do so.
1. Beware fake websites
If you do a search online you may well find that the top links are commercial sites that will charge you just for passing the form on. The correct address for any government service always ends in gov.uk and this one is at http://www.hmrc.gov.uk/sa/file-online.htm.
Read more about self-assessment tax scams.
2. If you haven’t paid through self-assessment before then you must register
See http://www.hmrc.gov.uk/sa/register.htm. Normally you will then be sent a Unique Tax Reference (UTR) number and an Activation Code by post. They will take a few days to arrive – so do it now!
3. Once you have your UTR and Activation Code you can log-on to online filing
The online form asks why you are doing self-assessment and which parts are relevant and only shows you the questions necessary for your circumstances.
Make sure you have all the information you need to answer them. You can save the form and return to it later if you need to look something up or work something out but it is better to have the information ready first.
Make sure you get to the final stage and the form is actually filed. If you have problems or questions call the self-assessment helpline 0300 200 3310. Charges are the same as normal 01 and 02 numbers which is some comfort if you are kept hanging on for a long time.
Read out guide to six taxes you can legally avoid.
4. The form will work out the tax due
That should be paid by January 31. If you have enough money in your bank account the best way to pay is by direct transfer. That will happen at once so you can pay on the last day – subject to your bank’s direct transfer limits – and it will still be in time.
If you pay online by debit card or credit card it goes through BillPay and takes three banking days so do it by January 28. There is no extra charge for paying by debit card but if you use a credit card there is a 1.4% surcharge to cover the costs HMRC pays to your card provider.
Remember: whatever your circumstances if you are due to file a tax return and have not done it, then do it now – or risk a £100 fine on February 1.