It’s November, and you still haven’t touched your self-assessment tax return. Perhaps you’ve been putting it off, maybe your records are a mess, or you’ve simply been too busy. Whatever the reason, you’re now staring down the barrel of the 31st January 2026 deadline with panic setting in.

Take a deep breath. You’re not alone, HMRC receives over 10 million returns, and a staggering number arrive in the final week of January. Whilst leaving it late isn’t ideal, it’s absolutely not too late to get this sorted.

This guide will walk you through exactly what to do when you’re behind schedule, how to prioritise your time, and crucially, how to avoid the costly penalties that await those who miss the deadline entirely.

Is it really too late to file on time?

No, it’s not too late, but you need to act immediately. Even if you’re reading this in early January, you still have time to file before the 31st January deadline, but you must start now.

Here’s the reality: HMRC’s online system accepts returns right up until midnight on 31st January. However, leaving it until the final day is risky. Technical issues, forgotten passwords, and missing information can derail last-minute filers.

The absolute worst thing you can do is give up and assume you’ll just pay the penalty. That £100 immediate penalty is just the start, it escalates rapidly, and you’ll also face interest on any unpaid tax.

What should I prioritise first?

When you’re behind schedule, working smart beats working hard. Here’s your priority order:

Priority 1: Check you can actually access HMRC’s system

Log into your Government Gateway account NOW. If you’ve forgotten your password, reset it today, the recovery process can take time. If you’ve never filed before and don’t have a UTR (Unique Taxpayer Reference), you need to register by 5th October, but contact HMRC immediately anyway.

Priority 2: Gather your income information

You absolutely cannot file without knowing your income. Focus on:

• P60s from any employment.
• Bank statements showing all income received.
• Invoices or payment records if you’re self-employed.
• Interest statements from savings accounts.
• Dividend vouchers from investments.

Don’t worry about perfect organization yet, just get the numbers.

Priority 3: Identify your major expenses

If you’re self-employed, you’ll need expense figures. Focus on the big categories first:

• Office/workspace costs.
• Vehicle/travel expenses.
• Professional fees and subscriptions.
• Major equipment purchases.

You can estimate some smaller categories if necessary, HMRC allows reasonable estimations when precise figures aren’t available, though you should mark them as provisional.

Priority 4: Everything else

Capital gains, pension contributions, Gift Aid donations; these matter, but get the basics done first. You can always amend your return later if needed.

How can I speed up the information gathering process?

Time is your scarcest resource right now, so work efficiently:

Use digital shortcuts: Download bank statements and credit card transactions electronically. Many banking apps let you export data directly. This is faster than rifling through paper statements.

Focus on categories, not individual receipts: If you’re missing some receipts, categorise what you have and make reasonable estimates for gaps. HMRC understands that records aren’t always perfect, what they won’t tolerate is obvious fabrication.

Use HMRC’s calculator tools: The HMRC website has calculators for expenses, mileage, and National Insurance. These save time and reduce errors.

Contact people who owe you information: Chasing down a missing P60 or investment statement? Phone them today. Explain the urgency. Most organisations can provide duplicate statements quickly.

Consider what you can reasonably claim: Don’t waste hours tracking down a £50 expense when you could use that time completing the return. Focus on material amounts.

What if my records are incomplete or missing?

This is surprisingly common, and whilst it’s not ideal, it’s manageable. Here’s what to do:

For missing bank statements: Contact your bank immediately. Most can provide statements going back years, often via online banking within minutes.

For lost receipts: If you genuinely made the purchase but lost the receipt, you can:

• Check if you have credit card or bank statements showing the transaction.
• Contact the supplier for a duplicate receipt or invoice.
• Make a reasonable estimate based on similar purchases (but note this on your records)

For incomplete mileage logs: If you didn’t keep detailed logs, reconstruct what you can:

• Review your diary or calendar for business trips.
• Check emails confirming meetings or site visits.
• Estimate based on typical weekly business mileage.

For unclear expenses: When in doubt, don’t claim it. It’s better to pay slightly more tax than to face penalties for overclaiming.

Should I estimate figures or wait for exact information?

This is a judgement call, but here’s the general rule: estimate if you must, but only reasonably.

HMRC explicitly allows estimates when:

• Exact figures would be disproportionately time-consuming to obtain.
• The estimates are reasonable and based on genuine business activity.
• You clearly mark them as estimates in your records.

However, wildly inaccurate estimates that happen to reduce your tax bill will trigger investigations. If your turnover was realistically around £45,000 but you estimate it at £30,000 to stay under a threshold, that’s not a reasonable estimate, that’s fraud.

Best practice: Use bank statements as your baseline for income (these are hard facts), and estimate expenses conservatively if needed.

How do I file my return as quickly as possible?

Once you have your information, filing is relatively straightforward:

1. Use the online service: It’s faster than paper and gives you instant confirmation. The system also auto-calculates tax, reducing errors.

2. File in sections: You don’t need to complete everything in one sitting. The online system saves your progress, so you can return to it.

3. Have all reference numbers ready:

• Your UTR (Unique Taxpayer Reference)
• National Insurance number
• Government Gateway credentials
• Any previous year’s figures (for comparison)

4. Follow the system prompts: HMRC’s system is actually quite intuitive. Answer each section honestly and completely. Don’t overthink it.

5. Double-check key figures: Before submitting, verify:

• Total income matches your records.
• National Insurance number is correct.
• Bank details for refunds are accurate.
• You’ve claimed major expenses.

What if I genuinely cannot finish by 31st January?

If you’ve tried everything and simply cannot complete your return by the deadline, here’s what you need to know:

There are no extensions: Unlike some countries, HMRC does not grant deadline extensions except in exceptional circumstances (serious illness, bereavement, etc.).

File what you can: It’s better to submit an incomplete but reasonable return on time and amend it later than to miss the deadline entirely. You can amend returns for up to 12 months after the filing deadline.

The penalties are automatic: Even one day late triggers a £100 penalty. Don’t assume you can sweet-talk your way out of it.

Payment is separate from filing: If you file on time but can’t pay, you’ll avoid the late filing penalty but still face interest on unpaid tax. This is better than facing both penalties and interest.

Can I get professional help at short notice?

Yes, but you need to be strategic about it. Many accountants are overwhelmed in January, so:

Contact multiple firms immediately: Don’t wait for callbacks, the clock is ticking. Explain your situation clearly and ask if they can take on urgent work.

Be prepared to pay premium rates: Rush jobs command higher fees, which is fair given the pressure you’re putting on the practice.

Have your information ready: Even if you’re paying for help, the accountant still needs your income and expense information. Gather what you can before meeting them.

Consider outsourcing specialists: Firms like Integra specialise in high-volume, rapid turnaround work and may have more capacity than traditional high-street accountants during peak season.

What about accountancy firms drowning in last-minute returns?

If you’re an accountancy practice reading this because you’re overwhelmed with client returns, you’re facing a different but equally urgent challenge.

The January rush creates a perfect storm:

• Clients arriving with shoeboxes of receipts.
• Staff working unsustainable hours.
• Quality suffering under time pressure.
• Risk of missing deadlines for multiple clients.

This is exactly when outsourcing becomes not just helpful but essential.

Why do smart firms outsource their last-minute work?

Even the best-planned practices get caught out by late clients. Outsourcing provides:

Immediate additional capacity: Scale up processing power within days, not weeks.

Consistent quality despite pressure: Dedicated teams maintain standards even with high volumes.

Protection for your team: Prevent burnout by distributing the workload.

Client service continuity: Senior staff focus on complex queries whilst routine returns are processed efficiently.

Risk mitigation: Professional oversight reduces the error rate that rises when everyone’s exhausted.

Firms using outsourcing report that January becomes manageable rather than dreaded and their teams don’t need two weeks to recover afterwards.

People Also Ask

Q1. What time does the self-assessment deadline close?
A1. The deadline is midnight on 31st January. However, HMRC’s systems can become slow in the final hours due to high traffic. Aim to file by 10 PM to avoid last-minute technical issues that could push you past the deadline.

Q2. Can I submit my self-assessment return late and just pay the penalty?
A2. While you can submit late, the penalties escalate quickly beyond the initial £100. After three months, it’s £10 per day (up to £900), then additional penalties at six and twelve months. Plus, you’ll pay interest on unpaid tax. It’s almost always cheaper to file on time.

Q3. What happens if HMRC’s website crashes on deadline day?
A3. If HMRC’s systems experience technical difficulties on deadline day, they may waive late filing penalties, but this isn’t guaranteed. Don’t rely on system failures, file earlier. If issues do occur, document them with screenshots as evidence.

Q4. Can I amend my tax return after filing if I find mistakes?
A4. Yes, you can amend your return within 12 months of the filing deadline (so by 31st January 2027 for 2024/25 returns). Use your Government Gateway account to submit amendments. If the change means you owe more tax, you’ll pay interest from the original deadline.

Running out of time? We can help you make the deadline

Whether you’re an individual struggling to complete your return or an accountancy practice buried under last-minute client submissions, time is the one thing you don’t have.

Integra specialises in rapid-turnaround self-assessment work without compromising quality. We’ve been helping UK taxpayers and accountancy firms meet January deadlines since 2004, and we understand exactly what you’re going through right now.

Emergency Self-Assessment Support

• 48-hour express service available for urgent returns.
• UK-qualified supervisors reviewing every submission.
• AI-powered accuracy checks catching errors in real-time.
• Work accepted until mid-January,  we can still help.
• Secure data handling ISO 27001 certified systems.
• 70% cost saving vs hiring emergency temporary staff.
• Guaranteed deadline compliance, we’ve never missed a client deadline.

Don’t Let the Deadline Beat You

The 31st January 2026 deadline is approaching fast, but you don’t have to face it alone. Whether you need us to handle your entire return or just take some of the volume off your overwhelmed team, we’re here to help.

Don’t spend the last weeks of January in panic mode. Don’t risk £100+ penalties that escalate into thousands. And don’t burn out your team trying to achieve the impossible.

Smart firms know when to ask for help. The question is: are you ready to be smart about this?

Visit: www.globalintegra.co.uk

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