If you started trading, took on a rental or picked up untaxed side income in the 2025 to 2026 tax year, the next date that matters is not January. It is 5 October 2026. That is the deadline to tell HMRC you need to complete a Self Assessment tax return — and you must do it before you can file online.

This guide is for Wigan and North West sole traders, landlords and anyone with untaxed income who is new to Self Assessment, or who sat out last year and now needs to come back in. It follows current GOV.UK guidance. If you are unsure whether you are in scope, check first — then register in time.

The 5 October deadline — what it actually is

GOV.UK is clear. You must tell HMRC by 5 October 2026 if you need to complete a tax return for the previous tax year (6 April 2025 to 5 April 2026) and you have either:

• not sent a tax return before; or
• registered before but did not need to send a tax return for the tax year 2024 to 2025.

You tell HMRC by registering for Self Assessment. If you tell HMRC after 5 October 2026, you could get a penalty. Registration is not filing the return. It is the step that gets you a Unique Taxpayer Reference (UTR) so you can start the return properly.

HMRC has upgraded the online registration service. Through a Personal Tax Account you can get your UTR in your online account within 72 hours, instead of waiting up to 15 days by post — provided you leave enough time before the deadlines that follow.

Who usually needs to register for 2025 to 2026

You must send a tax return if, in the last tax year, any of the following applied:

• you were self-employed as a sole trader and earned more than £1,000 before reliefs;
• you were a partner in a business partnership;
• you had Capital Gains Tax to pay when you sold or disposed of something that increased in value;
• you had to pay the High Income Child Benefit Charge and do not pay it through PAYE;
• you are an off-payroll worker repaying a student or postgraduate loan.

You may also need a return if you had untaxed income such as rent, tips and commission, savings interest, dividends or foreign income. HMRC’s recent reminder also flags new partners and anyone with untaxed income over £2,500.

If you are not sure, use HMRC’s free tool to check if you need to send a tax return. Guessing wrong and ignoring registration is how late penalties start.

Sole traders and side hustles

The £1,000 figure is gross trading income, not profit after expenses. A second-job plumber, hairdresser, courier or online seller in Standish or Skelmersdale who cleared just over that threshold still needs to register. If you already registered for another reason but have now started trading, GOV.UK says register again as a sole trader so Class 2 National Insurance is set up correctly.

Our sole trader support covers records, registration and the return for people who would rather not wrestle with HMRC’s screens alone.

Landlords and rental income

Property has its own thresholds. GOV.UK says contact HMRC if rental income is more than £1,000 a year, up to £2,500. You must report it on a Self Assessment return if it is more than £2,500 after allowable expenses, or more than £10,000 before allowable expenses. If you do not usually send a return, register by 5 October following the tax year you had the rental income. That catches plenty of North West landlords whose first buy-to-let or rising rents in 2025 to 2026 tipped them over the line.

After you register: paper 31 October, online 31 January

Once you are registered, the filing calendar for the 2025 to 2026 return is:

• Paper tax return — HMRC must receive it by 11:59pm on 31 October 2026, or you get a late filing penalty.
• Online tax return — submit by 11:59pm on 31 January 2027.
• Tax payment — pay what you owe by 11:59pm on 31 January 2027.
• Collecting the bill through your tax code — submit the online return by 11:59pm on 30 December 2026, or you will have to pay another way.

You can start the return any time from 6 April 2026. Most people file online; paper brings the deadline forward by three months. If you registered before but did not send a return for 2024 to 2025, you may need to reactivate your account first — GOV.UK warns that filing without reactivating can delay the return.

What if you miss 5 October?

Do not wait until January and hope. If you register after 5 October 2026, HMRC will send a letter or email giving you three months from that date to file. You must still pay any tax by 11:59pm on 31 January 2027, or you will get a penalty. Late registration shrinks your filing window and leaves the payment date fixed — so register now, get the UTR, then gather figures calmly.

A short checklist before 5 October

1. Confirm you need a return — use the GOV.UK checker, especially if your only extra income is rent, interest, dividends or a small trade.
2. Register or reactivate — sole traders register as self-employed; people who are not self-employed (for example many landlords) use the non-self-employed route, including form SA1 where that still applies.
3. Keep records tidy — invoices, bank statements, mileage, property expenses and any P60 or interest certificates for 2025 to 2026. Steady bookkeeping now makes January a check, not a panic.
4. Decide paper or online — if you are set on paper, work backwards from 31 October; otherwise aim online and leave January free for payment planning.
5. Estimate the bill early — you do not need a perfect figure to start budgeting. Ring-fence cash so 31 January does not empty the trading account.

Self Assessment is not the same as a Simple Assessment letter. Simple Assessment is HMRC calculating tax it already knows about and asking you to pay. Self Assessment is you telling HMRC about income that needs a full return.

For a wider refresher, see our guide to Self-Assessment for Income Tax. On the risks of filing late, our note on the consequences of missing Self Assessment deadlines is still worth a read.

Talk to CMA before the October cut-off

CMA Accountancy helps sole traders, landlords and small limited companies across Wigan, Appley Bridge, Standish and the wider North West. If you need to register, reactivate an old account, or want someone else to handle the 2025 to 2026 return, we can take it from here through our personal tax work and wider services.

See who we help, call 01257 255521, email [email protected], or use our contact page. We are at 39 Skull House Lane, Appley Bridge, Wigan WN6 9DR. Register by 5 October — then file with time to spare.