Can I complete my own Self Assessment tax return?

Completing your own Self Assessment tax return is entirely legal and widely done. HMRC's online service is free and guides you through each section. Millions of individuals file without professional help each year.

Before you can file online, you need a Government Gateway account linked to your Self Assessment record and a Unique Taxpayer Reference (UTR). If you have not filed before, register at HMRC's website and allow up to ten working days for your UTR to arrive by post.

For most limited company directors with a straightforward situation, the key information you need is: your P60 or payroll summary showing PAYE salary received; dividend vouchers for dividends taken from your company; bank interest statements; details of any pension contributions; and Gift Aid donations. The return then calculates your tax automatically.

The main sections a director completes are employment income, dividends, interest, and any additional income sources. The personal allowance for 2025/26 is £12,570 and it stays at £12,570 for 2026/27. Basic rate income tax at 20% applies on income from £12,571 to £50,270. Higher rate at 40% applies from £50,271 to £125,140. The additional rate at 45% applies above £125,140.

Dividends are taxed at separate rates. The dividend allowance for 2025/26 is £500, meaning the first £500 of dividend income is tax-free. Above the allowance, dividends falling in the basic rate band are taxed at 8.75%, in the higher rate band at 33.75%, and in the additional rate band at 39.35%. From 6 April 2026 (the 2026/27 tax year) the basic and higher rates rise to 10.75% and 35.75%.

One important area that catches many directors out is the tapering of the personal allowance above £100,000 of adjusted net income. For every £2 of income above £100,000, £1 of personal allowance is withdrawn. This creates an effective marginal tax rate of approximately 60% on income between £100,000 and £125,140. If your income is in this range, it is worth getting advice on whether pension contributions can reduce your adjusted net income below £100,000 and restore the full allowance.

A straightforward director's return with salary, dividends, and a small amount of interest can realistically be completed in under four hours. HMRC provides detailed help text on every field within the online return. The SA302 tax calculation summary is generated automatically after submission and can be used as proof of income for mortgages.

Situations where professional input is worthwhile include: income above £100,000; capital gains on property, shares, or other assets; foreign income or offshore accounts; SEIS or EIS investments; cryptocurrency transactions; redundancy payments; and significant pension contributions where annual allowance carry-forward is relevant.

The most common DIY errors are: omitting bank interest that has risen above the personal savings allowance (£1,000 for basic rate taxpayers, £500 for higher rate, £0 for additional rate in 2025/26); missing benefits in kind recorded on a P11D filed by your employer; and not checking whether dividends from overseas companies attract a different tax treatment.

You can amend a submitted return online up to twelve months after the 31 January filing deadline. After that, you must write to HMRC. Keep all records supporting your return entries for at least five years after the 31 January filing deadline, as HMRC can open an enquiry within twelve months.

AccountsOS can pre-populate your key figures from your company's records and present a summary for you to review before filing.