Can I Do My Own Self Assessment Tax Return in the UK? (2026 Guide)

Yes, you can absolutely do your own Self Assessment tax return in the UK. HMRC provides a free online portal that anyone can use to file their return directly, no accountant required. Millions of sole traders, freelancers, and business owners file their own returns every year without any professional help. Whether it is the right choice for you depends on how straightforward your income and expenses are, how confident you feel with numbers, and how much time you have. This guide gives you an honest, no-nonsense answer to help you decide.

What Does “Doing Your Own Self Assessment Tax Return” Actually Mean?

A Self Assessment tax return is a form you submit to HMRC each year to report your income, claim allowable expenses, and work out how much tax you owe. When people ask, “Can I do my own self-assessment tax return?” they are really asking whether they need to pay someone else, like an accountant or tax adviser, to do it for them.

The short answer is no, you do not need to. HMRC’s online Self Assessment system at gov.uk is designed for individuals to use themselves. It walks you through each section, only shows you the parts relevant to your situation, and calculates your tax bill automatically once you enter your figures.

That said, “can I” and “should I” are two different questions. For some people, filing their own return is perfectly sensible. For others, particularly those with more complex finances, professional help is worth paying for.

Is It Easy to Do Your Own Self Assessment Tax Return?

This depends entirely on your situation. For some people, it is genuinely straightforward. For others, it can be confusing and time-consuming. Here is an honest breakdown.

When Filing Your Own Return Is Relatively Simple

If most of the following apply to you, filing your own return is very manageable:

• You are a sole trader with one main source of income
• Your annual turnover is below £85,000 (so you only need to enter total income and total expenses — not a full breakdown)
• Your expenses are straightforward, things like phone bills, mileage, equipment, and software subscriptions
• You do not have rental income, foreign income, capital gains, or significant investment income to declare
• You have been self-employed for at least one full tax year and have kept basic records throughout

In this case, sitting down with your income and expense figures and working through HMRC’s online portal usually takes a couple of hours at most.

When Filing Your Own Return Gets Complicated

Filing your own return becomes harder and riskier if:

• You have multiple income sources (self-employment, employment plus rental income, for example)
• Your turnover is over £85,000, and you need to report a detailed breakdown of expenses
• You sold a property, shares, or another asset and need to declare capital gains
• You have foreign income or assets held abroad
• You are a company director with dividends and a salary
• You are behind on previous years and need to catch up
• You made a loss and want to carry it forward or offset it against other income
• You are part of a business partnership

In these situations, the return is not technically impossible to do yourself, but the risk of getting something wrong, and either underpaying tax (which HMRC will chase) or overpaying (which means losing money unnecessarily), increases significantly.

Can I Do My Own Tax Return Without an Accountant?

Yes. There is no legal requirement to use an accountant to file a Self Assessment tax return. HMRC’s free online service is available to everyone and is the most widely used method of filing in the UK.

Here is what you need to file your own return:

What You Need to Get Started

1. A Unique Taxpayer Reference (UTR): This is a 10-digit number HMRC assigns when you register for Self Assessment. If you do not have one, you need to register at the GOV Portal. HMRC posts your UTR within 10 working days of registration.

2. A Government Gateway account: This is your login for HMRC’s online services. If you do not already have one, you can create it at HMRC Self Assessment Tax Return. You will need to verify your identity using your National Insurance number and either a passport, driving licence, or payslip.

3. Your income records for the tax year

• Sales invoices or a record of total income received
• Bank statements (to cross-check figures)
• Any P60 or P45 if you also had employment income

4. Your expense records

• Receipts, invoices, or bank records for all business costs
• Mileage log if you are claiming vehicle expenses
• Home working records if claiming the home office allowance

5. Any other income details

• Savings interest statements from your bank
• Dividend vouchers, if you received dividends
• Rental income and costs if you let a property

Once you have all of this, you log in to your HMRC account, select “Complete your tax return” for the relevant tax year, and work through the sections one by one.

What Happens If You Make a Mistake Filing Your Own Return?

This is one of the main concerns people have about filing without professional help, and it is a fair one.

The good news is that HMRC allows you to amend your return online up to 12 months after the original filing deadline. So if you realise you made an error after submitting, you can log back in and correct it.

If the error is genuine and not deliberate, HMRC generally treats it reasonably. However, if an underpayment of tax results from a mistake, even an innocent one, you will owe the tax plus interest, and potentially a penalty depending on the circumstances.

The most common errors people make when filing their own return are:

• Claiming expenses that are not wholly and exclusively for business purposes
• Forgetting to include all income sources (bank interest, small freelance jobs, etc.)
• Not understanding Payments on Account, the advance payments HMRC requires toward next year’s bill, once your tax bill exceeds £1,000
• Choosing the wrong accounting method (cash basis vs accruals)
• Entering figures in the wrong boxes on the form

None of these mistakes is catastrophic if caught early, but they can create unnecessary hassle and costs.

How Much Does It Cost to Do a Self-Assessment Tax Return?

Doing It Yourself – Cost: Free

Using HMRC’s online portal to file your own Self Assessment tax return costs nothing. The service is free to use, and HMRC provides guidance notes alongside every section to help you understand what is being asked.

There are some optional paid tools, accounting software like QuickBooks, FreeAgent, Xero, or Sage, that can make the bookkeeping side easier throughout the year and help you prepare your figures before filing. These typically cost between £10 and £35 per month on a subscription basis, though many offer free trials.

If your affairs are simple, you do not need any of these. A basic spreadsheet tracking your income and expenses monthly is enough to prepare your figures for HMRC.

Using an Accountant – Typical Cost

If you decide to use an accountant or tax specialist to file on your behalf, the cost varies depending on the complexity of your return and who you use.

These are general market ranges. Prices in London tend to be higher; online accountancy services and smaller local firms often charge less.

It is also worth noting that accountant fees are themselves an allowable business expense, meaning you can deduct the cost of your accountant from your taxable profits, which reduces the actual after-tax cost to you.

Is Paying an Accountant Worth It?

For straightforward returns, probably not — especially if your accounts are well-organised. For more complex situations, a good accountant will often save you more in tax than their fee costs, simply by knowing which reliefs and allowances apply to your situation that you might not be aware of.

A useful way to think about it: if you are spending more than 3–4 hours trying to work out your return, becoming stressed about whether you have got it right, or if your financial situation is complicated, the time and peace of mind that an accountant provides is worth something.

How Do I Do a Self-Assessment of Myself? – Step by Step

Here is a practical walkthrough of how to complete your own Self Assessment tax return from start to finish.

Step 1 – Register for Self Assessment (If You Have Not Already)

If this is your first time filing, register at HMRC’s Portal. Choose the option that matches your situation, most commonly “I am self-employed” or “I am not self-employed, but I have other taxable income.”

HMRC will post your UTR number within 10 working days. You cannot file without it, so do this well before the deadline.

New to Self Assessment? Register by 5 October, following the end of the tax year you need to report. For the 2024/25 tax year, that means registering by 5 October 2025.

Step 2 – Set Up Your Government Gateway Login

Go to HMRC website and either log in with your existing details or create a new account. You will be asked to verify your identity, have your National Insurance number and a form of ID ready.

Once logged in, link your UTR to your account. HMRC will send a verification code by post, so do not leave this to the last minute.

Step 3 – Gather Your Records

Before you touch the form, get all your figures together. This is the step most people underestimate.

For the 2025/26 tax year (6 April 2024 to 5 April 2025), you will need:

• Total business income (sales/turnover) received during the tax year
• Total allowable business expenses
• Any other income (employment, rental, savings, dividends)
• P60 from your employer if you were also employed
• Pension contribution records
• Gift Aid donation receipts (if any)

Common allowable expenses for sole traders:

What you cannot claim:

• Personal meals (unless you are away from home overnight for work)
• Everyday clothing (only uniforms or specialist protective wear)
• Personal purchases mixed with business spending
• Fines or penalties

Step 4 – Log In and Start Your Return

Log in to your HMRC Government Gateway account and click “Complete your tax return”. Select the correct tax year.

HMRC’s system is broken into sections. Answer the initial questions, and the system will only show you the sections relevant to you; you will not have to wade through pages that do not apply.

Step 5 – Work Through Each Section

The main form (SA100) has sections for:

Personal details, your name, address, and National Insurance number (pre-filled in most cases).

For income from self-employment, you will complete the SA103 supplementary pages here. Enter your turnover (total income from your business) and your total allowable expenses. If your turnover is below £85,000, you can enter a single total for all expenses rather than a breakdown.

Employment income, enter the figures from your P60 if you had a job alongside your self-employment.

Other income, bank interest, dividends, rental income, pension income.

Tax reliefs, claim your pension contributions, Gift Aid, and any other reliefs.

Step 6 – Review the Tax Calculation

Once your figures are in, HMRC calculates your tax bill automatically. You will see:

• Your total income for the year
• Your Personal Allowance deduction (£12,570 for 2024/25)
• Your taxable income
• Income Tax owed at the basic rate (20%), higher rate (40%), or additional rate (45%)
• Class 4 National Insurance (6% on profits between £12,570 and £50,270; 2% above that)
• Any Payments on Account due

Check this carefully. If the figure looks much higher or lower than you expected, go back and check whether you have entered all your income and expenses correctly.

Step 7 – Submit and Note Your Confirmation

When you are satisfied with everything, click “Submit”. HMRC will give you a submission confirmation with a reference number. Save or screenshot this, it is your proof of submission.

Key deadlines:

Step 8 – Pay Your Tax Bill

Submitting your return and paying your tax bill are two separate steps. After submitting, pay what you owe by 31 January using:

• Online banking (BACS or Faster Payments), use HMRC’s bank account details and your UTR as the reference
• Debit card through your HMRC account
• Direct Debit (set up in advance through your HMRC account)

If you cannot pay in full, contact HMRC before the deadline to arrange a Time to Pay agreement or a monthly payment plan. HMRC is generally reasonable if you approach them proactively.

Should I Do My Own Return or Use an Accountant?

Use this as a quick guide to help you decide:

What Are the Risks of Doing Your Own Self-Assessment Return?

Doing your own return is not without risk. The main ones to be aware of are:

Underpaying tax, if you miss income or overclaim expenses, you will owe the shortfall plus interest, and potentially a penalty if HMRC opens an enquiry.

Overpaying tax is equally common, and something people do not think about. If you do not know all the allowances and reliefs you are entitled to, you may pay more tax than you need to. HMRC will not volunteer this information; it is up to you to claim what you are owed.

Penalties for errors, if HMRC considers an error to be due to “careless” behaviour, they can apply a penalty of up to 30% of the unpaid tax on top of the tax itself.

Time cost, for some people, the hours spent doing the return themselves could be better spent on income-generating work. If you earn £50 an hour and your return takes six hours, that is £300 worth of your time, potentially more than an accountant would charge.

Can I Do My Own Self Assessment Tax Return – Summary

Yes, you can, and millions of people do every year using HMRC’s free online portal. If your finances are straightforward and your records are organised, filing your own return is completely achievable.

The key is preparation: gather all your figures before you sit down with the form, understand what you can and cannot claim as expenses, and submit well before the 31 January deadline.

If your situation is more complex, or you simply want the peace of mind that everything has been done correctly, a professional service does not have to be expensive.

Need a Helping Hand With Your Self Assessment?

At Cheap Tax Returns, we offer affordable Self Assessment filing for sole traders, freelancers, and business owners across the UK. Whether you want someone to handle everything from start to finish or just check over your figures before you submit, we are here to help.

No jargon, no inflated fees, just straightforward tax help at a price that makes sense.

Get a quote today and take the stress out of your tax return.