Completing your self-assessment tax return can feel like a big task, especially if you’re doing it for the first time. But with the right preparation, organisation, and awareness of what HMRC expects, the process becomes far more manageable. Here are practical tips to help you file accurately, avoid common pitfalls, and keep the experience stress-free.
Start early, and keep good records all year round
One of the most common mistakes taxpayers make when completing their self-assessment tax return is leaving everything until January. Although the online submission deadline is 31 January, HMRC opens the self-assessment window as soon as the tax year ends on 5 April.
Good habits throughout the year make all the difference. Setting aside time each week or month to file receipts, update mileage logs, reconcile bank transactions, and record any income or allowable expenses prevents everything piling up at the last minute. Whether you prefer a well-organised physical folder or a digital system, consistency is key. Simple steps like labelling documents clearly, keeping digital copies of important paperwork, and using accounting software to automate routine tasks can save hours when January comes around, and gives you the confidence that nothing has been missed.
HMRC also encourages early filing as it gives you more time to check details, correct errors, and plan for any upcoming tax bill.
Is a self-assessment tax return right for you?
A self-assessment tax return is used to report personal income that isn’t automatically taxed through PAYE. This includes self-employment income, rental income, dividends, foreign earnings, or certain benefits.
It’s important to distinguish this from a company tax return, which is only relevant to limited companies and other incorporated entities. Company directors may need to complete both, depending on their personal income. Read more about the different types of tax returns.
Prepare the right information before you begin
Gathering everything in advance avoids delays and prevents mistakes. HMRC advises assembling:
- Your National Insurance number
- Your Unique Taxpayer Reference (UTR)
- Your P60 and P11D (if you’re employed)
- Details of all income sources, including self-employment, rental income, dividends, and savings interest
- Bank statements
- Pension contributions
- Gift Aid donations
- Invoices, receipts, and allowable expenses
- Mileage logs, if relevant
The more comprehensive your documentation, the easier it is to avoid omissions.
Don’t miss commonly overlooked income and allowances
Many taxpayers unintentionally under-report their income because certain categories are easy to overlook. Common ones include:
- Savings interest, this must be declared if it exceeds your Personal Savings Allowance
- Dividends, even small amounts, count
- Gift Aid donations, declaring these can boost your tax relief
- Self-employment expenses, only claim what you can evidence clearly
Being conservative and only claiming for expenditure you can fully justify helps reduce the risk of HMRC queries.
Break the self-assessment process into manageable steps
If you’re filing for the first time, it’s normal to feel a little overwhelmed. HMRC offers online guides and step-by-step tools, but it also helps to break the task into simple sections:
- Income
- Expenses
- Allowances and reliefs
- Final check and submission – you can save your submission as you go so that you can do a final check at the end
You can save and return to your online return at any time, making it easier to manage in stages.
Stay up to date with tax changes
Tax rules, thresholds, and digital filing requirements evolve regularly. Making Tax Digital (MTD) continues to be phased in, and although not all taxpayers are yet required to comply, preparing early, particularly by adopting MTD-compatible software, is strongly advised. Find out more about Making Tax Digital.
HMRC updates its guidance throughout the year, so keeping an eye on changes can prevent errors and ensure you’re claiming what you’re entitled to.
Know when to seek professional support
You should consider professional advice if:
- You have multiple income streams
- You’ve recently become self-employed
- You earn foreign income
- You run a limited company
- You’re facing an HMRC enquiry
Self-assessment tax return accountants add value by guiding you through the rules, ensuring nothing is missed, and potentially saving you money through proper tax planning. Using an accountancy firm also signals to HMRC that your return has been checked by a qualified accountant, and your accountant will handle any questions or enquiries that may arise on your behalf.
If you’d like support with your self-assessment or simply want reassurance that everything has been completed correctly, and that you only pay what you owe, no more and no less, our team is here to help.