Getting Started with Self Assessment: How and When to Register

Understanding Self Assessment Registration

If you’re earning income outside of PAYE — like from self-employment, property letting, or side hustles — you may need to register for Self Assessment to report it to HMRC.

Anyone needing to file a 2024/25 tax return must register for Self Assessment by 5 October 2025. Registering late can lead to penalties, so it’s best not to delay. Once you register, HMRC will send your Unique Taxpayer Reference (UTR) and Notice to File, which you’ll need to submit your return.

You can register yourself or ask your accountant or tax agent to handle it for you.

Do You Need to Register?

You must register if you’ve earned new untaxed income in 2024/25. This might include:

• Starting a new business or side hustle

• Renting out a property or offering holiday lets

• Earning freelance or consulting income

However, if your total income from self-employment or property letting is under £1,000 (before expenses), you don’t need to register thanks to the trading and property allowances.

If you rent out a furnished room in your home, you can also earn up to £7,500 tax-free (£3,750 each if shared).

To be sure, use HMRC’s online tool to check:
👉 www.gov.uk/check-if-you-need-tax-return

Already Registered Before?

If you registered for Self Assessment in the past but didn’t file a tax return for 2023/24, you’ll need to reactivate your account. Simply log in via your Government Gateway account.
If you can’t access it, fill out and send form CWF1 to HMRC to get started again.

How to Register Online

Register online through HMRC’s official site:
👉 www.gov.uk/register-for-self-assessment

Once submitted, it can take up to 21 working days for your registration to be processed and confirmed — so don’t leave it until the last minute!

Filing Deadlines to Remember

The deadline to submit your 2024/25 online tax return is 31 January 2026.
You don’t have to wait until January — filing early helps you plan and avoid stress.

If you get your Notice to File after 31 October 2025 (but registered on time), you’ll have three months from the notice date to submit your return.

Paying Your Tax

Any tax owed for 2024/25 must be paid by 31 January 2026.
If your bill is over £1,000, and less than 80% of your tax was collected through PAYE, you’ll also need to make a payment on account for the next year. This equals 50% of your current year’s tax and Class 4 National Insurance.

Key Takeaway

Registering for Self Assessment early ensures you have your UTR, avoids penalties, and gives you plenty of time to prepare your return. Whether you’re self-employed, a landlord, or earning side income — acting early keeps you stress-free and compliant.