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The 10 essentials to complete your Self-Assessment tax return for 2024/25

Completing a Self Assessment tax return is much easier when you have all the right information to hand before you start. Whether you’re employed, self-employed, a landlord, investor or someone with multiple income sources, gathering your documentation early can help you avoid mistakes, reduce last-minute stress and ensure you don’t miss anything important.

To help you prepare, here’s a checklist of the key details you’re likely to need when completing your tax return for the 2024/25 tax year.

1. Your Unique Taxpayer Reference (UTR)

Your 10-digit UTR is essential for filing your return and identifying you within HMRC’s Self Assessment system. You can usually find it on previous tax returns, HMRC letters, your Personal Tax Account or within your tax software.

If you’ve never filed before, allow time to register with HMRC. It can take up to 10 working days to receive your UTR.

2. Your National Insurance number and personal details

Make sure your National Insurance number, address and personal details are correct and up to date. HMRC uses these to calculate your National Insurance liability and verify your identity.

You’ll typically find your NI number on payslips, P60s or official HMRC/DWP documents.

3. Employment income and benefits from PAYE work

If you were employed at any point during the tax year, you’ll need details of:

→ P60 – showing your income and tax deducted for the full tax year (if still employed on 5 April)
→ P45 – if you left employment during the year
→ P11D – listing any taxable benefits (e.g. company car, private medical insurance)

If you download the official HMRC app and register for a GOV.UK account you should be able to access all these details online.

4. Self-employment income and business expenses

If you were self-employed, you will need:

→ Your total business income for the year
→ A breakdown of allowable business expenses
→ Dates of trading if you started or stopped within the tax year

You do not need to submit all your business transactions, nor copies of your business invoices and receipts, but you should keep them on record for 6 years in case HMRC ask for evidence.

5. Rental income from property

If you rent out a property, you’ll need:

→ Total rental income received during the tax year
→ Allowable expenses such as letting fees, mortgage interest, repairs, insurance and service charges
→ Details of any void periods or co-ownership arrangements

Your letting agent (if you use one) may provide statements periodically that summarise your rental income and expenses.

6. Bank interest and savings income

Most banks and building societies no longer deduct tax at source, so you’ll need to report gross interest received in the tax year. Information can usually be found via online banking statements or annual interest statements.

Remember to include only your share of any jointly owned accounts. ISAs are tax-free and can be ignored.

7. Dividend income from shares or investments

If you own shares in a company (including your own limited company), you’ll need dividend vouchers or statements showing the date and amount of each dividend paid and the total dividends received during the year.

Investment platforms and wealth managers usually provide statements that summarise your dividends for the tax year.

8. Capital gains from selling assets

If you sold or disposed of assets such as shares, cryptoassets, second properties or other chargeable items, you may need to report capital gains.

→ Keep records of purchase and sale dates
→ Document acquisition and disposal values
→ Include any allowable costs such as legal fees and stamp duty

Even if your gain is below the annual exempt amount, you may still need to declare it depending on the total value of your asset disposals.

9. Pension contributions, Gift Aid and other tax reliefs

You may be entitled to extra tax relief on some payments you’ve made, including personal pension contributions and charitable donations under Gift Aid. 

Charities usually provide receipts or acknowledgments of donations made, including confirmation that Gift Aid was claimed.

10. Foreign income and other taxable sources

If you received income from outside the UK - including overseas employment, foreign pensions, rental income or investment returns - you may need to include it in your return.

Some foreign income may be taxable in both the UK and overseas, so having full details helps determine whether double taxation relief applies.

Final thoughts

Having the right information prepared before you begin makes completing your Self Assessment return far smoother. It helps prevent missed income, forgotten reliefs or incorrect entries.

Using reliable tax return software like TaxCalc, can guide you through each section of the tax return, prompting you for the right information to help ensure nothing is missed.

For a simpler way to file your tax, download TaxCalc’s award-winning tax return software today!

Learn more here.