Timeline to Register Self Assessment Tax Return

As the 5 October 2025 HMRC Self Assessment registration deadline approaches, it’s time to ask yourself one important question:

Do I need to register for Self Assessment this year?

If your answer is “I’m not sure” — you’re not alone. In fact, figuring out who needs to register can be surprisingly complicated. HMRC guidance uses the words “must,” “may,”and “should” — and it all depends on your income sources, thresholds, and even where you live.

So, if you’re new to the UK tax system or just unsure, don’t guess. Ask an accountant.

What is the 5 October Deadline?

If you received untaxed income during the 2024/25 tax year (which ended on 5 April 2025), and you've never filed a Self Assessment tax return before, you must register by 5 October 2025 to avoid penalties.

Registering late could lead to delays, fines, and stress you don't need. As we move closer to tax season, HMRC systems and phone lines get busier, so now’s the time to act.

Could Registering Incorrectly Cost You? So… Who Needs to File a Self Assessment Tax Return?

You may need to file a tax return if you earn untaxed income, but what counts as “untaxed” can vary. For example, many people with rental income, self-employment, dividends, savings, or foreign income may fall under the Self Assessment system. But depending on the amount, the nature of your income, or whether you’ve received a notice to file, the answer might not be so straightforward.

In some cases, earning more than £1,000 from self-employment or rental property may mean you’re required to file. In others, having multiple income sources — even if you pay tax through PAYE — could trigger the need to report. Directors of companies who receive dividends, landlords who let out properties part-time, or even individuals receiving foreign pensions or interest may also fall into this group. Then there are more complex situations, such as non-resident landlords or people living abroad with UK income — they often ask us if a return is needed.

What makes things more complicated is that sometimes, even if no tax is due, HMRC still requires a return for reporting purposes. At other times, people assume they don’t need to file — and then get an unexpected letter from HMRC.

There are rules. There are thresholds. But there is no universal checklist that applies to everyone. That’s why it’s best to get proper advice.

We’ll be publishing a separate post soon covering the topic in more depth — Who needs to file a Self Assessment tax return, and who doesn’t? If this is something you’re wondering about, stay tuned and follow our UK tax blog so you don’t miss it.

So... Could Registering Incorrectly Cost You? Yes, registering when you don’t actually need to can also be inappropriate. It could lead to unnecessary costs and trouble. So it’s important to make sure you’re doing the right thing from the start.

Filing Isn't Always Optional — But It's Not Always Obvious

Unfortunately, HMRC doesn’t always make it crystal clear to taxpayers that they are required to file a return. As the name suggests, this is a Self Assessment tax return — not an HMRC assessment tax return. The law specifies that the taxpayer himself is the sole and only one who needs to file and report their income situation accurately and pay tax. That is, the authority may not know you’ve made a mistake — until they find out and catch you. Then it becomes a compliance and penalty matter. That’s why we often say: if you’re unsure, speak to a professional.

We’re a team of qualified accountants who deal with UK Self Assessment tax returns every day — for individuals, landlords, sole traders, non-residents, and company directors.

Not Sure Whether You Need to Register?

We get it. The rules are complex.That’s why we’re here to help.

Get in touch with us to review your situation. We’ll advise whether you need to register, and handle the entire process for you — from registration, to preparing and submitting your tax return.

Follow Us for More

We’ll be posting a detailed breakdown soon on who needs to file a Self Assessment tax return and who doesn’t — so follow our UK Tax Blog (elagaaccountancy.com) if you want clear, accountant-approved guidance with real-life examples.

Ready to Register for Self Assessment?

If you think you may need to register, or just want peace of mind — now is the time to act. Accountants at Elaga will take care of the process from start to finish, so you avoid late penalties and stay compliant.

No More Guesswork. You Want Professional Guidance

If you have questions about Registration of Self Assessment Tax Return, contact Elaga Accountancy now, we’d be happy to assess your company’s situation and walk you through your options. Don’t rely solely on your gut feeling or a random forum post. The team at Elaga Accountancy brings years of real-world experience to help you make confident, informed decisions, aligned with both your business structure and personal goals.

***Contact us to learn more.

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