Literally everything you need to know before you start filling in your online self-assessment tax return

Carol Cheesman
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The deadline for self-assessment tax returns is on 31 January (Source: Getty)

Congratulations, you survived Christmas and New Year: time to put your feet up while waiting for the Rio Olympics? Nope.

The deadline for submitting your self-assessment tax return (SATR) online is 31 January. And there are penalties if you don’t make it, or if HM Revenue and Customs (HMRC) takes the view you haven’t taken enough care in completing it.

Apart from the later deadline (a paper SATR has to be submitted by 31 October), one of the great advantages of an online submission is that no signature is required—you’d be amazed how many unsigned documents HMRC receive—but there are plenty of other mistakes you need to avoid.

1. Don’t tick the wrong boxes.

Take your time. HMRC provides very helpful notes and explanations: read them. You may be able to build an Ikea flatpack without reading the instructions, but Ikea won’t fine you if you forget to include something vital.

2. Double check your calculations

It’s important to be accurate. While the HMRC software will add and subtract the figures you input, those figures need to be correct, so don’t shoe-box your records. Make sure you’re organised.

3. Paperwork

The paperwork you will need (where relevant) includes:

  • P60, P45 and P11D
  • Expense records
  • Benefits including maternity/paternity pay, statutory sick
  • pay, job seekers allowance
  • Pension records
  • Bank statements
  • Property income
  • Foreign income including evidence of tax already paid abroad
  • Capital gains
  • Employee share schemes
  • Student loan payments

If you are self-employed you will need:

  • Cash books
  • Invoices
  • Mileage records
  • Receipts
  • Bank statements
  • Records of all sales and takings, purchases and expenses
  • Money taken out of business for personal use (if any)
  • Personal money put into the business (if any)

4. Additional income

If you have additional income, you will need to include supplementary pages. This additional income may come from juggling fire at Covent Garden at weekends, or perhaps your Hunger Games fan-fiction has become an Amazon sensation, or it could be from investments, property, shares etc. Make sure you include all additional income on the supplementary pages.

5. Don’t claim the unclaimable

Check with an accountant as there are costly penalties for incorrect claims; and besides, there may be things you hadn’t thought of that can be claimed.

6. Don't sweat

It’s best to get things right first time, but the good news is, if you do make a mistake on your SATR you can correct it. You've normally got 12 months from January 31st after the end of the tax year to correct it. This is called an amendment. For example, for the 2015-16 return you have until 31 January 2018 to make an amendment.

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