Does The 5 October Self Assessment Registration Deadline Apply to You?

Who the 5 October Deadline Applies To

The 5 October deadline applies to anyone who had untaxed income during the 2025/26 tax year and has not yet notified HMRC. The most common situations are:

Online sellers. If you sold on Vinted, eBay, Etsy, Depop, Amazon or any other platform and your activity was trading, that is buying to resell for profit rather than clearing out personal possessions, and your gross income from all platforms combined exceeded £1,000 in 2025/26, you need to register. If you are unsure whether your selling counts as trading, our guide to whether you owe tax on your Vinted sales walks through the five questions that determine the answer.

New sole traders. If you started self-employment in 2025/26 , as a freelancer, consultant, contractor or in any other self-employed capacity, and your gross self-employment income exceeded £1,000, you need to register by 5 October 2026.

People with multiple income sources. If you have a PAYE salary and also have self-employment or trading income above £1,000, you need to register. Your employer handles income tax on your salary through payroll, but the self-employment element needs to be declared separately through Self Assessment. Our guide to PAYE and self-employment in the same tax year covers how both income streams are treated together in the tax calculation.

Anyone with other untaxed income. Rental income, interest income above the Personal Savings Allowance, income from abroad and income from other sources that has not been taxed at source may all trigger a Self Assessment requirement depending on the amounts involved.

The deadline does not apply to people whose untaxed income was entirely below £1,000 in 2025/26. The £1,000 trading allowance is a gross income threshold. If your gross receipts from all self-employment and trading sources combined were below £1,000, you do not need to file a Self Assessment return for this year.

What the 5 October Deadline Actually Is

The 5 October deadline is the notification deadline, not the filing deadline. These are two different things and confusing them is one of the most common misunderstandings about the Self Assessment calendar.

Notification (5 October 2026): The deadline by which you must tell HMRC that you had untaxed income in 2025/26 that requires a Self Assessment return. This is done by registering for Self Assessment at gov.uk.

Filing (31 January 2027): The deadline by which you must submit your completed Self Assessment tax return online and pay any tax owed, along with the first payment on account if your bill exceeds £1,000.

Missing 5 October does not mean you cannot file. It means you notified HMRC late. The return still needs to be filed by 31 January 2027 regardless. But late notification is itself a compliance failure, and HMRC can apply a penalty for it. Registering now, four days before the deadline, puts you in the right position before any penalty exposure begins.

What Happens If You Miss the 5 October Deadline

Missing the 5 October deadline does not mean the situation is unmanageable. It means the window for penalty-free late registration has closed, but the practical path forward is the same.

HMRC's penalty for late notification of a chargeability to tax is based on the amount of tax that was due and unpaid. For a genuine oversight or innocent error, the penalty is typically nil or very low, particularly where the person comes forward voluntarily rather than being contacted by HMRC first. HMRC's own guidance distinguishes clearly between deliberate non-compliance and innocent failure to notify, and treats the two very differently.

The key principle is that voluntary disclosure after the deadline is always better than being contacted by HMRC. If you have missed 5 October, register now, calculate your tax position accurately and file as soon as your records allow. The earlier you act after a missed deadline, the better the outcome is likely to be.

One important note on HMRC's data. Under DAC7 reporting rules, HMRC already holds sales data from Vinted, eBay, Etsy, Depop and Amazon for sellers who crossed the reporting threshold of more than 30 transactions or approximately £1,740 in a calendar year. If you sold above those thresholds and have not registered, HMRC may already hold information that shows unregistered trading income. That is a further reason to act now rather than wait. For the full detail of what HMRC holds and why, our guide to Vinted, your National Insurance number and HMRC explains the reporting picture clearly.

What to Do Right Now: Four Steps

Step 1: Register at gov.uk today. Go to gov.uk/register-for-self-assessment and complete the online registration. The process takes around 10 minutes. You will need your National Insurance number, your address and basic details about your self-employment or trading activity. If you are also employed, have your P60 or payslip to hand as your employer's PAYE reference may be requested.

Step 2: Wait for your Unique Taxpayer Reference. HMRC sends your Unique Taxpayer Reference (UTR) by post. It takes up to 10 working days to arrive. You cannot file your Self Assessment return without it. Registering now means your UTR arrives well before the January deadline, giving you time to prepare and file without rushing.

Step 3: Gather your income and expense records. Pull together your income for the 2025/26 tax year from every source , platform transaction reports, bank statements, PayPal history and invoices. Then gather evidence of allowable expenses: stock purchases, postage, mileage records, phone bills, equipment receipts. If your records are incomplete, our guide to filing Self Assessment with no records covers how to reconstruct what you need from bank statements and platform reports.

Step 4: Calculate your bill and plan for January. Knowing the number matters as much as filing the return. Your Self Assessment bill is income tax plus Class 4 NI on your trading profit. If the bill exceeds £1,000, the first payment on account is due on the same day as the main bill in January. Your January total could be one and a half times your main bill. Our guide to payment on account explains exactly how this works and why it catches so many first-year filers by surprise.

The January Total: What You Are Actually Planning For

Most people who register late are also unprepared for the size of the January payment. Filing the return by 31 January 2027 is one obligation. Paying what is owed on that date is another. Both fall on the same day.

For a sole trader or online seller with a Self Assessment bill above £1,000, the January payment is the bill itself plus the first payment on account of 50% of the bill. A bill of £1,856 produces a January total of £2,784. A bill of £3,000 produces a January total of £4,500. The July payment on account of a further 50% follows six months later.

Jade's trading profit for 2025/26 was £9,280. Her Self Assessment bill was £1,856. Her payment on account was £928. Her January 2027 total was £2,784. She had not planned for it at the start of the year because she had not known the number. Once she registered, calculated her position and saw the figure, she had enough time to set aside the right amount before January. The time between registering now and January is not wasted time. It is planning time.

For the full list of expense categories that reduce your taxable profit before the bill is calculated, our guide to expenses sole traders commonly miss covers the seven most commonly overlooked categories. Claiming every allowable expense reduces the bill. Reducing the bill also reduces the payment on account. Both the January payment and the July payment on account of 50% due on 31 July 2027 become smaller.

The Most Important Thing

Registering before 5 October is better than registering after it. Registering after 5 October is better than not registering at all. Filing before 31 January 2027 is better than filing after it. And knowing your January total in October is better than discovering it in January.

The deadline is four days away. The registration takes ten minutes. The Unique Taxpayer Reference takes up to ten working days to arrive. The maths on timing work in your favour if you act today.