If you are filing online, here are our step-by-step tips on what everything means and how to actually do it:

1. Log in to your account – using your Government Gateway user ID and navigate to the “file your self assessment” page. You only have to input your UTR number once when you first register for online services.
2. Check your details are correct – for example, your address or marital status are up to date, as well as your date of birth, as this may impact on your allowances.
3. Follow HMRC’s lead – the system responds to the details you enter, so any parts that aren’t relevant, will be removed. You can’t progress either if you’ve not answered what HMRC wants.
4. Fill in your return – based on the answers you give, you will be presented with the sections that need to be completed. Your progress will be saved when you press “next”, so don’t worry if you need to go and find missing documents and are logged out.
5. Missing sections – if you realise that you have missed a section, you can click on the link on the right-hand side of the screen to navigate back.
6. Income warning – Under each section relating to income, you will be asked to enter the “gross income” plus any tax that may have already been deducted. Make sure that you do not enter the “after tax income” instead of the “before tax income”.
7. Have your invoices to hand – For the self-employed, when you enter your earnings you need your invoices to hand, to tot up everything you earned and enter your turnover before expenses are taken off. Any other income to add comes later on in the form.
8. Enter your expenses – there are strict rules here: they must be tax-deductible expenses related solely to your business.
9. For the employed – have your P60 ready and also your P11D if you have received any employee benefits during the year, such as a company car or medical cover. Fill in the figures directly from these documents; calculations aren’t needed.
10. Property rental income – if you rent out a property, you first need to enter the gross income received from rents, and then allowable deductions such as mortgage interest, to get to your rental profit for the year.
11. Partnership income – if you are a member of a partnership, you should have received or completed a partnership tax return. Your share of the partnership profit that is shown on that return will need to be entered on the partnership form, SA800. This is separate to the general self-assessment return. Any partnership expenses should have already been included on the partnership return.
12. Pension income – enter any state pension you have received during the tax year. This is paid every four weeks, so count 13 payments and not 12. You also need to include income from any private pensions. Each year, your pension provider will send a statement or P60 showing the gross amount paid and the tax deducted. Always enter the gross amount.
13. Other supplementary pages – if you have any other income not mentioned, such as capital gains, further supplementary pages must be completed. To report CGT, you need dates of ownership and sale, calculations for each capital gain or loss you report, and any details of price when you bought and sold the asset. Just continue through the links for other relevant pages to you and enter the information required.
14. Reliefs – if you have made any Gift Aid or charitable donations, have paid into a pension scheme and are a higher-rate taxpayer, or are able to claim any other reliefs, fill in the details to ensure you get the tax relief that applies.
15. The high income child benefit charge – if you are in receipt of child benefit and your income, or your spouse’s income, is in excess of £50,000, fill in this section. Enter the number of children for whom you receive the benefit, and how much you have got in the year. You may have to repay some or all of it and this will be included in the overall tax liability.
16. Extra questions – once you have filled in the relevant supplementary pages, there will be a few questions remaining. There are some mandatory questions for everyone concerning tax adjustments in the year such as underpaid tax that may have been included in your tax code – or if you’ve overpaid, you can tell HMRC how you want it to be repaid.
17. Supporting information – You also have a chance to add any further information that you might think relevant to support the figures in your tax return – although you don’t need to submit all your receipts to HMRC.
18. Check your form – once you have finished the return, it is time to check it thoroughly. All the sections you have completed will be displayed, giving you a final opportunity to check your figures prior to submitting.
19. View your calculation – this page shows how much tax you have to pay based on the figures that you have entered. It also shows the payments on account you need to make in January and July. If tax due is under £3,000, you may have the opportunity to have it collected through your PAYE tax code rather than paying HMRC in January. However, this can only be done if you submit your online return by 30 December.
20. Save your return – you can save a copy when you submit a self-assessment and return to your computer or print it off to keep with your paper records.
21. Submit your return to HMRC – once this is done, you will receive confirmation. Now you just need to make sure that you pay your tax on time – or set up a payment schedule – before the 31 January deadline. Check the homepage if you can’t remember how much you owe.
22. Get help – If you cannot pay your tax on time, contact HMRC on 0300 200 3822. This may save on penalties and late-payment interest. If you don’t think you’ll be able to submit your tax return by 28 February (HMRC has waived fines for anyone filing before then) – for reasons such as a mental or physical condition, or because you’re in hospital, or the victim of abuse – contact HMRC for advice on 0300 200 3310.

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