How to file a self-assessment online

Filing your tax return can seem like a daunting task. The aim of this guide is to help steer you through the process of submitting your tax return.

Following this guide will help you understand the steps involved in submitting your self-assessment and how to navigate the minefield of the website.

Whilst being self-sufficient is empowering; having a competent and qualified accountant prepare or at least check over your accounts before filing your tax return for you can add real value. Often, a good accountant will be able to save you the value of their fees many times over by reducing your tax bill.

Before you start

Do you need to complete a tax return?

You’ll need to submit a tax return if any of the following applied to you in the last tax year (6 April 2018 to 5 April 2019):

  • You’re self-employed and your income was more than £1,000.
  • Your income was more than £50,000, and you or your partner claimed child benefit.
  • You earned more than £2,500 from renting out property, or from other untaxed income such as tips or commission.
  • You earned more than £100,000 in taxable income.
  • You earned £10,000 or more before tax from savings, investments, shares or dividends.
  • You earned income from abroad, or lived abroad and had a UK income.
  • You need to pay capital gains tax.
  • You received income from a trust.
  • Your state pension was more than your personal allowance and was your only source of income (unless you started getting your pension on or after 6 April 2016).
  • HMRC has told you that you didn’t pay enough tax last year (and you haven’t already paid up through your tax code or voluntary payments).
  • You filed a self-assessment tax return last year (even if you didn’t owe any tax). You’ll need to do this unless HMRC has already written to you to say you don’t need to file one

If you are not sure whether you need to file a tax return, go to to fill in a short questionnaire to determine if you need to file a tax return or not.

Have you completed a self-assessment before? 

If so, and your self-assessment was previously completed by your accountant, you may not need to sign up again. Ask your accountant to provide your government gateway login information to allow you to submit your self assessment online. 

If not, you will need to sign up by going to:

Once you have signed up and registered, HMRC will send you an activation code to verify your account and a unique taxpayer reference number (UTR). 

This can take up to 10 days so make sure you leave yourself plenty of time!

Tax return Deadlines & Penalties for not filing your tax return.

If you:

  • Want to fill in a paper return, you must send it to HMRC by 31 October (or 3 months after the date on your notice to complete if it’s later)
  • Want to fill a tax return online; you must submit by 31 January (or 3 months after your notice to complete if that’s later)
  • If you are using your tax code to recover taxes owed to you, this must be submitted by 31 December.

The deadline for your tax bill or class 2 national insurance payments is 31 January.

If the HMRC does not receive your tax return by these deadlines, you will receive a £100 penalty. 

Further penalties will be charged if your return is more than 3, 6, and 12 months late.

What information do I need to help me file my tax return?

You are now ready to collate your documents to help you fill in the tax return. You may find the following documents helpful:

  • If you are self-employed you will need; profit and loss accounts, payslips or business records.
  • If you are an employee you will need; your P60, ‘End of Year Certificate’, ‘Employee Benefits Certificate or P45, P11Ds, payslips or P2, ‘PAYE Coding Notice’.
  • Your bank/building society statements, dividend advice, investment brokers’ schedules.
  • Personal pension contributions statements.

These records will not need to be sent to HMRC  unless requested so it is important that your records are held securely.

What expenses can I claim for?

If you are self-employed; it is likely that you will have incurred expenses in order to help you run your business. If these expenses meet the HMRC criteria for “allowable expenses” they can be used to reduce your taxable profits. Therefore, reducing the tax you are liable to pay. 

In general, for expenses to be considered allowable, it must be incurred exclusively as a result of operating your business.

Some common expenses that you may be entitled to claim for are:

  • Office costs or costs for using your home as an office
  • Salaries of staff and costs of subcontractors
  • Materials costs
  • Professional fees such as accountancy costs and legal fees
  • Costs of training
  • Insurance, bank charges as well as depreciation of machinery & other fixed assets.
  • Protective clothing or uniforms.
  • All or part of your telephone bill depending on business usage

There are many other potential allowable expenses but each will only be allowable in the context of the operations of the business. If you’re ever in any doubt it is always best to consult your accountant or contact the HMRC directly using the dedicated HMRC deadline.

HMRC telephone helpline: 0300 200 3310

Outside of the UK: +44 161 931 9070

Filing my tax return

If you are submitting a self-employed tax return, the HMRC has also provided a 1 hour long video that will take you through the process step by step.

There is a very useful step-by-step video by the HMRC on how to complete your tax return online

You can also find detailed explanations for each of the questions on the form in the  How to fill your tax return guide

Remember to pay your bill 

If you are not due a refund for overpaying tax, it is likely you will be required to make a payment to the HMRC. This will need to be paid before 31 January 2020.

You will be required to pay:

  • any outstanding taxes from 2018/19
  • plus half of the estimated tax bill for 2019/20.
  • The second half of the estimated tax bill will be due to be paid on 31 July 2020, with balancing payment due on 31 January 2021

This can be paid to the HMRC directly through your online gateway account. Additional payment methods can be found here.

If you are worried that you will not be able to pay your bill in time, you must contact the HMRC as soon as possible with a valid reason explaining why the payment will be late.

Payment Support Service Telephone number: 0300 200 3835

For more information

If you would like any further information regarding your tax return see the helpsheets provided by

Alternatively, book your free consultation with an us

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