New to Self Assessment? The 5 October 2026 Registration Deadline Is Approaching

A practical guide for new sole traders, landlords, business partners and people with untaxed income

Jassim Financial Solutions Ltd | Updated 1 October 2026

The Self Assessment registration deadline is approaching for people who need to complete a tax return for the first time for 2025/26. If you received income during the 2025/26 tax year that was not fully taxed through PAYE, you may need to complete a Self Assessment tax return. For people who have not filed before, the immediate issue is registration: HMRC says you should notify it by 5 October 2026 if you need to complete a return for the tax year ended 5 April 2026.

The registration date is not the same as the tax return filing deadline. Registering tells HMRC that you need to enter Self Assessment and allows the process to begin. The online filing and payment deadline for the 2025/26 return is 31 January 2027, but waiting until January to deal with registration and records can create unnecessary pressure.

Understanding the Self Assessment registration deadline early gives you time to organise your records and prepare for the next filing date.

Self Assessment Registration Deadline: Who Needs to Act?

You may need to register if one or more of the following applied between 6 April 2025 and 5 April 2026:

• You were self-employed as a sole trader and your gross trading income was more than £1,000 before expenses.
• You became a partner in a business partnership.
• You received rental income from property or land that needs to be declared.
• You received other untaxed income, such as tips, commission, savings income, dividends or foreign income.
• You disposed of an asset and may have Capital Gains Tax to report.
• You need to pay the High Income Child Benefit Charge and are not paying it through PAYE.

This is not a complete list, and the position depends on the type and amount of income received. HMRC provides an online checker for people who are unsure whether a return is required.

The 1000 pound allowance does not answer every question

A common misunderstanding is that every amount below £1,000 can simply be ignored. The trading allowance and property allowance can each provide relief of up to £1,000 in appropriate circumstances, but the rules differ depending on the source of income and whether the allowance is available.

For example, a sole trader whose gross trading income exceeds £1,000 will normally need to register. Someone with lower income may still choose or need to submit a return, such as to claim a loss, pay voluntary Class 2 National Insurance contributions, support a Tax-Free Childcare claim or establish self-employed income for Maternity Allowance.

Do not decide whether registration is required by looking only at profit. The £1,000 trading test is generally based on gross income before expenses.

What if you were registered before

If you previously registered for Self Assessment but did not need to submit a return for 2024/25, you may need to reactivate your account for 2025/26. Filing without reactivating can delay the return. If HMRC has already issued a notice requiring a tax return, that notice should not be ignored even if you believe no tax is due.

What information should you start collecting

Registration is only the first step. Starting the record-gathering process now will make preparation of the return more accurate and manageable. Depending on your circumstances, useful records may include:

• Sales invoices, platform statements and records of other business income.
• Receipts and invoices for business expenses.
• Business and personal bank statements relevant to the income being declared.
• Rental income statements and records of property expenses.
• P60, P45 and P11D documents.
• Dividend vouchers, savings interest statements and investment records.
• Details of asset disposals and the original purchase costs.
• Pension contributions and Gift Aid records where relevant.

Self-employed individuals generally need to keep business records for at least five years after the 31 January filing deadline for the relevant tax year. Records should be complete, readable and sufficient to support the figures reported.

What happens after registration

Meeting the Self Assessment registration deadline does not mean the tax return must also be submitted by 5 October. Once registration is completed, HMRC will provide or confirm your Unique Taxpayer Reference. You can then prepare the 2025/26 return, calculate the liability and plan for payment. The main online filing and payment deadline is 31 January 2027.

Filing earlier does not normally mean paying earlier, but it can give you more time to understand the amount due and manage cash flow. Some taxpayers may also have payments on account, so the amount payable in January can be higher than the balancing tax for the year alone.

What if the 5 October deadline is missed

If you realise after 5 October that you should have registered, take action promptly rather than waiting until January. A late notification does not remove the requirement to file or pay. HMRC states that a failure-to-notify penalty may arise in some circumstances, particularly where tax remains unpaid, although the outcome depends on the facts.

How Jassim Financial Solutions can help

Jassim Financial Solutions supports sole traders, landlords, business partners and individuals with Self Assessment registration and tax return preparation. We can help identify the information required, organise the records and prepare the return based on your circumstances.

If you are unsure whether you need to register for the 2025/26 tax year, contact Jassim Financial Solutions before the deadline to discuss your position.

This article provides general information only and is not a substitute for advice based on your individual circumstances.

Frequently asked questions

Is 5 October the deadline for submitting the tax return

No. It is the date by which certain people should notify HMRC that they need to complete a return. The online filing and payment deadline for 2025/26 is 31 January 2027.

Do landlords always need to complete Self Assessment

Not necessarily. The answer depends on the level and type of property income, available allowances and whether a return is required for another reason.

Do I register if I made a loss

You may choose or need to register if you want to claim relief for a trading loss. The appropriate treatment depends on your circumstances.

Can I file before January

Yes. Once you are registered and have the necessary records, you can submit the 2025/26 return before the January deadline.