How to Complete a Self Assessment Tax Return

If you need to complete a Self Assessment tax return, the job can look much worse before you start than it does once you break it into steps.

You need to know whether a return is required, gather the right information, complete the main return and any extra sections that apply to you, check the numbers and then deal with the tax bill.

That may not get the pulse racing, but a little preparation makes the process much less stressful.

About this episode

Completing a tax return is probably not high on anybody’s list of favourite ways to spend an afternoon.

For many people, it brings stress, delay and the temptation to leave it until later.

But once a Self Assessment return is required, it becomes one of those jobs that is much easier when you understand what HMRC is asking for.

In this episode, we look at who may need a return, what information to gather, how the return is structured, what to think about with business expenses, the main deadlines and what to do if you cannot pay the bill.

This is also the first part of a two-episode sequence. Here we deal with the wider Self Assessment return. Our self-employed tax return guide then looks specifically at the business section for sole traders and freelancers.

Who needs to complete a Self Assessment tax return?

Not everybody needs to file one.

HMRC uses Self Assessment where tax cannot simply be dealt with through systems such as PAYE.

Common situations include:

• you are self-employed as a sole trader and your gross trading income is more than £1,000
• you are a partner in a business partnership
• you need to report certain taxable capital gains
• you need to pay the High Income Child Benefit Charge and it is not being collected through PAYE
• you have untaxed income from property, commission, savings, dividends or overseas sources
• HMRC has asked you to submit a return

There are other circumstances as well, so do not rely on an old list you remember from several years ago.

If your circumstances have changed, check whether a return is still required.

Get your information together before you start

A smoother tax return starts with preparation.

Gather the information first instead of trying to find documents while you are halfway through the return.

Depending on your circumstances, this may include:

• your Unique Taxpayer Reference, or UTR
• employment details such as P60, P45 or P11D information
• self-employed business records and accounts
• property income and expense records
• savings and investment income
• dividend information
• pension contributions
• Gift Aid donations
• information about capital gains
• details of tax already deducted

Your UTR is the ten-digit number HMRC uses to identify you within Self Assessment.

If you are filing for the first time, register early enough to get the information you need before the filing deadline arrives.

The main return and supplementary pages

A Self Assessment return is not one giant box containing every possible type of income.

There is a main return, and then additional sections may apply depending on your circumstances.

The main return deals with your core personal and tax information.

Supplementary pages can then cover areas such as:

• employment
• self-employment
• business partnerships
• UK property
• foreign income or gains
• capital gains
• non-UK residence

You only complete the sections that are relevant to you.

If you are a sole trader or freelancer, the self-employment section is where the business income and expenses come into the return. We cover that in much more detail in our Self-Employed Tax Return guide.

Use records, not guesses

The figures on your tax return should come from records you can support.

Bank statements, invoices, bookkeeping records, payslips, pension information and other documents help build the picture.

If something is missing, investigate it.

Check your bank account. Look through credit card statements. Review invoices or your diary where appropriate.

Do not simply put your finger in the air and invent a number that feels about right.

If you genuinely need to use a provisional figure because the final information is not yet available, make sure you follow HMRC’s rules and correct the return when the final figure becomes known.

Business income and allowable expenses

If you are self-employed, your business profit feeds into Self Assessment.

Broadly, that means starting with your business income and deducting allowable business costs.

But not everything you spend while running a business automatically becomes a tax deduction.

The expense needs to meet the relevant business-use rules.

Take a trip to Disney because running the business has stressed you out, and you may have a very enjoyable time. That does not make the holiday a business expense.

Travel to meet a client for a genuine business purpose is a different matter.

Some costs sit in the middle.

Your mobile phone or computer may have both business and personal use. In those cases, you usually need to identify the appropriate business element rather than claiming the whole amount.

Our self-employed tax return guide goes further into income, expenses, cash basis, equipment and working from home.

Check the return before submitting it

Once the information is entered, take time to review it.

Check that all relevant income has been included.

Make sure you have not entered the same amount twice.

Look at the figures that seem unexpectedly high or low.

Review claims for expenses and reliefs.

Then ask whether the final tax calculation makes sense compared with what you expected.

Our guide to common tax return mistakes covers several areas worth checking before you press submit.

Self Assessment deadlines to remember

The exact tax year changes, but the normal Self Assessment timetable follows the same key dates.

5 October

If you need to complete a return for the previous tax year and you are filing for the first time, or need to reactivate Self Assessment after a gap, you normally need to tell HMRC by 5 October.

31 October

HMRC normally needs to receive a paper Self Assessment return by 31 October.

30 December

If you owe less than £3,000, already pay tax through PAYE and meet HMRC’s other conditions, submitting your online return by 30 December may allow HMRC to collect the bill through your tax code.

31 January

The normal deadline for an online Self Assessment return is 31 January following the end of the tax year.

Tax due under Self Assessment is normally payable by the same date.

If payments on account apply, there may also be a second payment on 31 July.

For more detail, see our guide to Payments on Account.

Filing early gives you more control

The filing deadline is the last date, not a target date.

Getting the return completed earlier tells you what the tax bill looks like and gives you more time to plan how you will pay it.

It also removes one more job from the back of your mind.

Filing the return early does not normally mean you have to pay the bill immediately.

What if you cannot pay the tax?

First, do not impersonate an ostrich.

Putting your head under the duvet, ignoring letters and hoping HMRC forgets about you is not a payment strategy.

Get the tax return filed so the amount due is clear.

Then contact HMRC as early as possible.

Depending on the circumstances, you may be able to arrange a Time to Pay plan rather than paying everything in one lump sum.

The important thing is to engage with the problem before interest, penalties and collection activity make the situation worse.

How to complete a Self Assessment tax return: checklist

1. Check whether you need a return. Do not assume the rules are the same as last year.
2. Register with HMRC if necessary. Make sure your Self Assessment account is active.
3. Gather your records. Get your UTR, income details, business records and supporting documents together.
4. Identify the sections you need. Complete the main return and the relevant supplementary pages.
5. Enter all taxable income. Make sure nothing has been accidentally left out.
6. Review expenses and reliefs. Claim what you are entitled to without turning personal costs into business deductions.
7. Check the calculation. Make sure the result looks reasonable.
8. Submit by the correct deadline. Paper and online returns have different filing dates.
9. Plan the payment. Check the amount due and whether payments on account apply.
10. Deal with payment problems early. Speak to HMRC rather than ignoring the bill.

FAQs

What do I need to complete a Self Assessment tax return?

You normally need your UTR plus records covering the income, tax deductions, expenses, reliefs and other information relevant to your circumstances.

Do all company directors need to submit a tax return?

No. Being a company director on its own does not automatically mean you need to submit a Self Assessment return. What matters is whether your income and circumstances create a filing requirement or HMRC asks you to file.

What are supplementary pages?

Supplementary pages are additional sections used to report types of income or gains that are not covered fully by the main return, such as self-employment, property, employment, foreign income and capital gains.

Can I submit my Self Assessment return before January?

Yes. You can normally submit it after the relevant tax year ends on 5 April. Filing earlier gives you more time to understand and prepare for the tax bill.

Can HMRC collect my tax through PAYE?

Potentially. If you owe less than £3,000, already pay tax through PAYE and meet the other conditions, HMRC may be able to collect it through your tax code if the return is filed by the relevant deadline.

What should I do if I cannot pay my Self Assessment bill?

Submit the return and contact HMRC as soon as possible. Depending on your circumstances, a payment arrangement may be available.

Episode Timecodes

• 00:00 – What this Self Assessment episode covers
• 01:39 – Why completing the return earlier helps
• 02:17 – Income and gains covered by Self Assessment
• 02:47 – Who may need to submit a tax return
• 04:32 – How the tax calculation works
• 05:02 – Main return and supplementary pages
• 05:41 – Information to gather before starting
• 06:51 – Using records and reasonable figures
• 07:24 – Self-employed profits and allowable expenses
• 08:06 – Mixed business and personal expenses
• 09:16 – Capital costs and simplified expenses
• 12:20 – Filing and payment deadlines
• 13:42 – What to do if you cannot pay
• 14:20 – Part one and the self-employed follow-up

Related episodes and guides

• Self-Employed Tax Return: What Sole Traders Need to Report
• Self Assessment Tax Returns
• Personal Tax Return Explained
• 5 Tax Return Mistakes to Avoid in Self Assessment

Key takeaway

Completing a Self Assessment tax return is much easier when you know what information you need before you begin.

Check whether you need to file, gather the records, complete the relevant sections, review the numbers and submit the return before the deadline.

Then make sure you understand the tax bill and how you are going to pay it.

You do not need to love tax returns.

You just need a process that keeps the numbers under control and stops January turning into a crisis.

Further Support

If you need help completing your Self Assessment, checking what you need to declare or understanding your tax bill, you can contact us for an initial chat.

You can also use our free online business calculators to support your tax and business planning.

For more practical finance and tax support, visit the I Hate Numbers YouTube channel, or listen and follow on Apple Podcasts.

📘 Book
https://www.ihatenumbers.co.uk/i-hate-numbers-book/

🎧 Podcast
https://www.ihatenumbers.co.uk/simplifying-accounting-and-tax-i-hate-numbers-podcast/

🌐 Website
https://www.ihatenumbers.co.uk