Submitting a Self-Assessment tax return: A Step-by-Step Overview

At Keith Graham Chartered Accountants, we recognise that figuring out how to submit a Self-Assessment tax return can be stressful, especially if this is a completely new system to you. That's why we've put together this simple, step-by-step guide with everything you need to know. Read on to make sure you are well-equipped to submit your next personal tax return efficiently and correctly.

How to submit a Self-Assessment tax return

Make a note of important deadline dates

Before you begin, note down the deadline dates you must pay attention to when submitting your self-assessment tax return. This will help you avoid penalties as a result of missed deadlines and late payments. The key dates to remember for the current tax year are:

  • 5th April: This is the official end date for every tax year.
  • 5th October: This is the deadline for registering for Self-Assessment tax purposes with HMRC.
  • 31st October: This is the deadline for submitting paper tax returns.
  • 31st January: This is the deadline for submitting online tax returns.

To make sure you meet these deadlines, decide in advance whether you would like to submit your Self-Assessment tax return to HMRC online or by post.

Register with HMRC to receive your UTR

If you haven't submitted a Self-Assessment tax return before, you will need to register with HMRC. This lets them know that you have accrued untaxed income during the current tax year and will generate your Unique Taxpayer Reference (UTR).

If you submitted a personal tax return for the previous tax year, you will need to use the same UTR this time.

You will need to open a Government Gateway account if you plan to complete your return online. Make sure to activate this at least a few weeks before the payment deadline to double-check your access.

Find the financial information you need to submit

Hopefully, you will have kept a record of any untaxed income you made during the reporting tax year. This will make the next step much easier!

If you haven't, now is the time to collect all the financial information needed to fill out your return, along with your UTR and National Insurance number.

You will also need to gather evidence of any expenses you made for self-employment purposes or any expenses that might be eligible for tax relief, such as pension contributions.

Download or open the SA100 tax return online

The next step of submitting a self-assessment is to start filling out the SA100 tax return form, which is something every self-assessed earner must complete. You can download the form from the Government's website to print, fill out and send to HMRC.

Alternatively, you can complete the form online. Completing Self-Assessment returns electronically is the easiest and most popular option.

Fill out the sections of the SA100 that apply to you

The SA100 tax form has clear instructions detailing exactly what you need to fill out. The form will ask you to provide information regarding your income, pension payments, annuities, state benefits, charitable contributions and any transactions eligible for tax relief. You may not need to complete every section, so read the notes to see which boxes apply to you.

Make sure to fill out the document carefully and double-check your details before finalising the form.

We recommend starting to fill out your tax return with plenty of time before the deadline. This gives you the freedom to check anything you aren't sure of with an experienced accountant.

Check whether you need to complete supplementary forms

After you complete the SA100, check whether you need to complete any supplementary forms. These contain additional questions about taxable income, capital gains tax and property income. Supplementary forms are necessary if you need to pay tax as a:

  • Company director
  • Self-employed worker
  • Business partner
  • Foreign national (or someone who has dual residency).

Or if you need to declare income from:

  • Capital gains
  • Property
  • Foreign income.

Pay any tax and National Insurance contributions owed

Once you've submitted or sent off your Self-Assessment tax return, HMRC will tell you how much tax you owe. If you submitted supplementary information as a self-employed earner, you will also need to pay National Insurance contributions.

Following this, it will be your responsibility to pay your tax bill by the deadline. HMRC accept payments by debit card, credit card, online transfer, telephone transfer or cheque.

Do you need advice on how to submit a Self-Assessment tax return?

For expert advice and guidance on filing out a Self-Assessment tax return, look no further than Keith Graham Chartered Accountants. With our professional approach to personal financing and friendly team of tax advisors, submitting tax returns has never been easier.

To learn more about our accounting services in Hampshire, contact our Aldershot accountants today. We're on hand to help with everything from Self-Assessment returns to retirement planning.