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Do You Need to Register for Self Assessment?

Posted on 7th September 2026 at 15:24

Starting a new business, taking on freelance work or earning income outside your usual salary can be exciting. But it can also bring new tax responsibilities, and one of the most important is knowing whether you need to register for Self Assessment.

For the 2025-2026 tax year, which ran from 6th April 2025 to 5th April 2026, anyone who needs to complete a tax return for the first time must tell HM Revenue & Customs (HMRC) by 5th October 2026. Understanding the rules now can help you avoid missed deadlines, unexpected penalties and a stressful rush later.

What Is Self Assessment?

Self Assessment is the system HMRC uses to collect Income Tax from people whose tax is not fully deducted automatically through PAYE. If you have income that HMRC needs you to report, you may need to complete a tax return after the end of the tax year.

Not everyone with additional income needs to register, so it is important to look at your individual circumstances rather than assume that a new income stream automatically means a tax return.

Who Needs to Register for Self Assessment?

You may need to register and complete a Self Assessment tax return if, during the tax year, you:

were self-employed as a sole trader and had gross trading income of more than £1,000 before expenses

were a partner in a business partnership

received taxable income from renting out property or land

received other untaxed income, such as tips, commission, savings interest, dividends or foreign income

needed to pay Capital Gains Tax on the disposal of an asset

needed to pay the High Income Child Benefit Charge and were not paying it through PAYE

There are other circumstances in which a return may be required, so if you are unsure, it is sensible to check your position with HMRC or speak to an accountant.

Starting a New Business or Side Hustle?

If you have recently started freelancing, consulting, selling services or running a side business, keep a close eye on your gross trading income. If your total gross trading income is more than £1,000 in a tax year, you will generally need to register for Self Assessment as a sole trader.

The £1,000 figure relates to income before deducting expenses, not your profit. This is an easy point to misunderstand when a small side project begins to grow.

What If You Receive Rental Income?

Becoming a landlord can also create a requirement to tell HMRC about your income. The property allowance can provide up to £1,000 of tax-free property income each tax year, but the reporting requirements depend on the level of rental income and your wider circumstances.

If you have started letting a property, a room or another form of accommodation, do not wait until January to work out whether you need to declare it. Keeping clear records of rent received and relevant property costs from the beginning will make your tax affairs much easier to manage.

What Counts as Untaxed Income?

You may be employed and already pay tax through PAYE but still need to complete a tax return because of income received elsewhere.

Examples can include:

income from freelance or casual work

rental income

tips or commission not taxed through payroll

certain savings and investment income

dividend income

foreign income

The rules and allowances vary depending on the type and amount of income involved. If you have more than one source of income, getting advice early can help you understand what needs to be declared.

When Do You Need to Register?

If you need to complete a tax return for the 2025/26 tax year and you have not sent one before, you should tell HMRC by 5th October 2026.

You may also need to reactivate your Self Assessment account if you were registered previously but did not need to submit a return for the 2024/25 tax year.

Once registered, the online filing deadline for the 2025/26 tax return is 31st January 2027, and any tax due must also normally be paid by that date.

What Happens If You Miss the Registration Deadline?

If you realise after 5th October that you should have registered, do not ignore it. Register as soon as possible and make sure you understand the filing and payment deadlines that apply to you.

HMRC may charge a penalty where a failure to notify results in tax being unpaid, so taking action promptly can help prevent the situation from becoming more complicated.

Start Keeping Records from Day One

Good record-keeping is one of the simplest ways to make Self Assessment easier. If you are starting a new venture, create a system for your financial records straight away rather than trying to recreate everything months later.

Depending on your circumstances, you may need to keep:

invoices and sales records

receipts and evidence of business expenses

bank statements

rental income and property expense records

records of other income received

Clear, accurate records can make preparing your tax return more straightforward and help ensure you do not overlook income or allowable costs.

Don't Wait Until January to Think About Your Tax Bill

Registering for Self Assessment is only the first step. It is also worth planning for the tax you may need to pay.

Having a plan and setting aside money regularly can make the 31st January payment deadline easier to manage. Filing your return early can also be helpful because you will know how much you owe sooner and have more time to budget your finances.