Introduction
Tax deadlines are one of those things that seem far away until they’re suddenly tomorrow.
Missing a deadline costs you money in penalties and interest. It also creates stress you don’t need. The good news is that staying on top of deadlines isn’t complicated once you know what they are and when they happen.
I’m David from Green & Moore Accountancy. I’ve helped hundreds of UK small businesses navigate tax deadlines without the panic. This guide gives you every important date for 2026, what each one means, and how to prepare for it.
No confusion, just the dates you need and what to do about them.
How to Use This Guide
Bookmark this page. Set reminders in your calendar for the deadlines that apply to your business. Not every deadline will be relevant to you.
Quick reference:
- Sole traders and partnerships – Focus on Self-Assessment dates
- Limited companies – Focus on Corporation Tax and PAYE dates
- VAT-registered businesses – Add VAT deadlines to your list
Read through, mark what applies to you, and you’re sorted.
Self-Assessment Tax Deadlines 2026
These apply if you’re self-employed, a sole trader, or a partner in a partnership.
5 April 2026 – End of Tax Year 2025/26
This isn’t a deadline for filing anything, but it’s important. This is the last day of the current tax year.
Any income or expenses you want to count for tax year 2025/26 must happen by this date. After 6 April 2026, you’re into the 2026/27 tax year.
What to do:
- Make sure all invoices are sent or received before this date if you want them in this tax year
- Check you’ve claimed all allowable expenses
- Review pension contributions (they can reduce your tax bill)
5 October 2026 – Register for Self-Assessment
If you need to file a Self-Assessment tax return for the first time for tax year 2025/26, you must register by this date.
This applies if you:
- Became self-employed during 2025/26
- Started earning over £1,000 from self-employment or rental income
- Need to declare income HMRC doesn’t already know about
What to do: Register online at gov.uk/register-for-self-assessment. You’ll get a Unique Taxpayer Reference (UTR) number. You need this to file your return.
Don’t leave this until October. Register as soon as you know you need to. HMRC can take weeks to send your UTR.
31 October 2026 – Paper Tax Return Deadline
If you’re filing a paper tax return for tax year 2025/26, it must reach HMRC by this date.
Most people file online now because it’s faster and gives you an extra three months. But if you’re filing on paper, this is your deadline.
What to do: Complete your SA100 form and post it to HMRC. Allow time for postal delays. Sending it on 30 October is cutting it too close.
31 January 2027 – Online Tax Return and Payment Deadline
This is the big one. Most people file online, which means your deadline is 31 January 2027 for tax year 2025/26.
You must:
- File your Self-Assessment tax return online
- Pay any tax you owe
- Pay the first payment on account for 2026/27 (if applicable)
What to do: Don’t wait until January. File early if you can. HMRC’s systems get overwhelmed in late January, and you don’t want technical problems to make you late.
If you owe tax, you can pay online immediately or set up a payment plan if you’re struggling. HMRC is more helpful if you contact them before the deadline, not after.
Payment on account explained: If your tax bill is over £1,000, you’ll need to make two payments on account for the following year. The first one is due on 31 January alongside your tax bill. It’s half of what you owed last year.
31 July 2026 – Second Payment on Account
If you made payments on account for tax year 2025/26, the second payment is due on 31 July 2026.
This is half of your previous year’s tax bill. It goes toward your 2025/26 tax liability. Any difference gets settled when you file your return in January 2027.
What to do: Pay online through your Government Gateway account. Set a reminder so you don’t forget. This deadline catches people out because it’s in the middle of summer when everything else is quiet.
Penalties for Missing Self-Assessment Deadlines
HMRC doesn’t mess around with late filing or payment.
Late filing penalties:
- 1 day late: £100 fine (even if you owe no tax)
- 3 months late: £10 per day (up to £900)
- 6 months late: £300 or 5% of tax owed (whichever is higher)
- 12 months late: Another £300 or 5% of tax owed
Late payment penalties:
- Interest charged from 1 February
- 30 days late: 5% of tax owed
- 6 months late: Another 5%
- 12 months late: Another 5%
These add up fast. A £2,000 tax bill paid 6 months late will cost you an extra £260 in penalties and interest.
Making Tax Digital for Income Tax Self-Assessment (MTD ITSA)
If you’re self-employed or a landlord, there’s a major change coming that affects how you report your income to HMRC. It’s called Making Tax Digital for Income Tax Self-Assessment.
What Is Making Tax Digital?
Making Tax Digital means keeping your tax records digitally and submitting updates to HMRC through compatible software. You already have to do this if you’re VAT-registered. Now it’s coming for income tax too.
Instead of filing one tax return each January, you’ll submit quarterly updates throughout the year showing your income and expenses.
When Does It Start?
The rollout is happening in stages based on your income:
From 6 April 2026:
- Self-employed individuals and landlords with income over £50,000 must join MTD ITSA
- This affects tax year 2026/27 onwards
From 6 April 2027:
- Self-employed individuals and landlords with income over £30,000 must join
- This affects tax year 2027/28 onwards
If your income is under the threshold, you don’t need to worry about this yet. But keep an eye on announcements because the threshold will drop.
Who Needs to Use MTD ITSA?
You need to join if you’re:
- Self-employed (sole trader)
- In a business partnership
- A landlord with property income
Your total income from these sources determines when you must join. This is your gross income before expenses, not your profit.
You don’t need to join if:
- Your income is below the threshold
- You only have PAYE employment income
- You’re already managing everything through a limited company
How MTD ITSA Works
Instead of one annual tax return, you’ll submit quarterly updates showing:
- Income received in that quarter
- Expenses paid in that quarter
- Any other relevant information
The quarters are:
- 6 April to 5 July
- 6 July to 5 October
- 6 October to 5 January
- 6 January to 5 April
You submit each update within one month of the quarter ending.
Then at the end of the tax year:
- You submit a final declaration
- HMRC calculates your tax bill
- You pay any tax owed by 31 January (same as now)
What Software Do You Need?
You must use MTD-compatible software. You can’t just use spreadsheets or submit updates manually through the HMRC website.
Popular options for sole traders:
- Xero
- QuickBooks
- FreeAgent
- Sage
- FreshBooks
Many of these offer packages specifically for sole traders starting from around £10-15 per month. Some have free tiers for very simple businesses.
Your accountant can also handle this for you using their software. Ask them about their MTD service.
Key MTD ITSA Deadlines for 2026/27
If you’re joining MTD ITSA from 6 April 2026 (because your income is over £50,000), here are your deadlines:
Quarter 1 (6 April – 5 July 2026):
- Submit update by: 5 August 2026
Quarter 2 (6 July – 5 October 2026):
- Submit update by: 5 November 2026
Quarter 3 (6 October 2026 – 5 January 2027):
- Submit update by: 5 February 2027
Quarter 4 (6 January – 5 April 2027):
- Submit update by: 5 May 2027
Final declaration and payment:
- Submit final declaration by: 31 January 2028
- Pay tax owed by: 31 January 2028
What About the Annual Tax Return?
The annual Self-Assessment tax return will eventually be phased out and replaced entirely by the quarterly updates and final declaration.
During the transition, you might need to do both for a while. HMRC will confirm exact requirements closer to the time.
Penalties Under MTD ITSA
HMRC will use a points-based penalty system similar to VAT:
Late submission:
- Each late quarterly update adds a point
- Reach your threshold (likely 4 points) and you get a financial penalty
- Points reset after a period of compliance
Late payment:
- Interest charged from the payment deadline
- Penalties apply for continued non-payment
The exact penalty amounts haven’t been finalized yet, but they’ll be similar to the current Self-Assessment penalty structure.
How to Prepare for MTD ITSA
If you’re joining in April 2026, start preparing now:
1. Get your records digital
- Start using accounting software today
- Stop relying on shoeboxes of receipts
- Get into the habit of recording income and expenses weekly
2. Choose your software
- Research MTD-compatible options
- Many offer free trials
- Pick one that suits your business type
3. Learn the basics
- Most software is designed for non-accountants
- Watch tutorial videos
- Many providers offer free training
4. Consider getting help
- An accountant can set everything up for you
- They can handle the quarterly submissions
- One-off setup fee plus ongoing monthly or quarterly service
5. Sign up for updates
- Register on the HMRC website for MTD updates
- Rules and requirements might change
- Better to know early than be caught out
Common Questions About MTD ITSA
“Can I still use spreadsheets?”
You can use spreadsheets to organize your thinking, but you must submit updates through compatible software. HMRC won’t accept spreadsheet uploads.
“What if I miss a quarterly deadline?”
You’ll get penalty points. Too many points trigger financial penalties. Keep on top of the deadlines.
“Do I need to submit updates if I had no income that quarter?”
Yes. You still need to submit an update showing £0 income. Skipping quarters counts as late submission.
“What if my income drops below the threshold?”
Once you’re in MTD, you generally need to stay in it. Check with HMRC if your circumstances change significantly.
“Will my accountant handle this for me?”
Most accountants offer MTD services. Ask yours what they provide and what it costs. Some include it in existing fees, others charge separately for quarterly work.
“Is this really necessary?”
Yes. Once you meet the threshold, MTD is mandatory. There’s no opting out. HMRC wants everyone reporting digitally.
The Positives of MTD ITSA
This feels like extra work, and initially it is. But there are benefits:
Better cash flow planning: You’ll know your tax position quarterly instead of getting a shock in January.
Fewer year-end surprises: Regular updates mean fewer forgotten expenses or lost receipts.
Easier to spot problems early: If your income drops or expenses spike, you’ll see it in real time.
Potentially smaller tax bills: Quarterly reporting makes it easier to claim everything you’re entitled to.
Modern systems: Most MTD software connects to your bank and categorizes transactions automatically. It’s actually less work than manual spreadsheets once you’re set up.
MTD ITSA Resources
Official HMRC guidance:
- gov.uk/guidance/making-tax-digital-for-income-tax-self-assessment
- Check here for the latest requirements and deadlines
Software providers:
- Most have MTD-specific pages explaining how their systems work
- Many offer free trials so you can test before committing
Your accountant:
- Ask them about MTD services
- Get a quote for setup and ongoing quarterly support
Corporation Tax Deadlines 2026
These apply if you run a limited company.
9 Months After Year End – File Company Accounts
You must file your annual accounts with Companies House within 9 months of your company’s financial year end.
Example:
- Year end: 31 March 2026
- Accounts deadline: 31 December 2026
What to do: Your accountant usually handles this. Make sure they have all the information they need well before the deadline. Chasing missing receipts in November when your deadline is December creates unnecessary stress.
12 Months After Year End – File Corporation Tax Return and Pay Tax
You have 12 months from your year end to file your Corporation Tax return (CT600) with HMRC. But you only have 9 months and 1 day to pay any tax you owe.
Example:
- Year end: 31 March 2026
- Pay tax by: 1 January 2027
- File return by: 31 March 2027
What to do: Don’t wait until month 12 to file. The payment deadline comes much sooner. If you haven’t calculated your tax bill by month 9, you won’t know how much to pay.
File early. Pay on time. Avoid penalties.
Corporation Tax Penalties
Late filing:
- 1 day late: £100
- 3 months late: Another £100
- 6 months late: HMRC estimates your tax and adds 10% penalty
- 12 months late: Another 10% penalty
Late payment:
- Interest charged from day 1
- Gets expensive quickly on larger tax bills
VAT Deadlines 2026
These apply if you’re VAT-registered. Your deadlines depend on whether you’re on standard quarterly filing or monthly filing.
Standard Quarterly VAT Deadlines
Most businesses file quarterly. Your deadline is one month and 7 days after your VAT quarter ends.
2026 VAT quarter deadlines:
Quarter ending 31 January 2026:
- File and pay by: 7 March 2026
Quarter ending 30 April 2026:
- File and pay by: 7 June 2026
Quarter ending 31 July 2026:
- File and pay by: 7 September 2026
Quarter ending 31 October 2026:
- File and pay by: 7 December 2026
What to do: File online through HMRC’s Making Tax Digital (MTD) compatible software. You can’t file VAT returns on paper anymore unless you have an exemption.
Pay electronically. Cheques aren’t accepted for VAT.
Monthly VAT Deadlines
Some businesses file monthly. Your deadline is one month and 7 days after the month ends.
What to do: Same process as quarterly, just more frequent. Most accounting software can handle this automatically if you keep your records updated.
VAT Penalties
HMRC changed the penalty system in 2023. It’s now points-based.
How it works:
- Each late submission or payment adds a point
- Reach your threshold (varies by filing frequency) and you get a £200 penalty
- Each further late submission while at threshold adds another £200
- Points expire after a penalty-free period
Late payment:
- Interest charged from day 1
- 15 days late: 2% penalty on outstanding amount
- 30 days late: 2% penalty on outstanding amount
- Plus ongoing daily penalties after 31 days
PAYE Deadlines 2026
These apply if you employ people or pay yourself through PAYE as a company director.
19th of Every Month – Pay PAYE and National Insurance
If you employ people, you must pay HMRC the income tax and National Insurance you’ve deducted from wages by the 19th of each month (22nd if you pay electronically, which you should).
2026 payment deadlines:
- January 2026 wages: Pay by 19 February 2026
- February 2026 wages: Pay by 19 March 2026
- March 2026 wages: Pay by 19 April 2026 (And so on through the year)
What to do: Most payroll software calculates this automatically. Set up a direct debit to pay HMRC so you never miss a deadline.
19th of Every Month – Submit Full Payment Submission (FPS)
Every time you pay employees, you must submit an FPS to HMRC. This must be done on or before the pay date.
What to do: Your payroll software does this automatically when you run payroll. Just make sure you run payroll before you actually pay your staff.
19 May 2026 – End of Year PAYE Submissions
By 19 May 2026, you must submit:
- Final Full Payment Submission for tax year 2025/26
- Employer Payment Summary (EPS) if applicable
- P60s to employees by 31 May 2026
What to do: Your payroll software handles the submissions. You need to give P60s to anyone employed on 5 April 2026. This shows their total pay and tax for the year.
PAYE Penalties
Late payment:
- 1-3 months late: 1% of amount owed
- 4-6 months late: Another 1%
- 7-9 months late: Another 1%
- 10+ months late: Another 1%
- Plus interest on top
Late filing:
- Points-based system similar to VAT
- Penalties escalate with repeated late filings
Other Important Dates for 2026
1 March 2026 – P11D Deadline
If you provide benefits to employees (company car, health insurance, etc.), you must file P11D forms by 6 July 2026 for the tax year ending 5 April 2026.
What to do: Keep records of all benefits provided throughout the year. Don’t try to remember everything in June.
6 April 2026 – New Tax Year Starts
Tax rates, allowances, and thresholds can change on this date. Check what’s changing so you’re not caught off guard.
Common changes:
- Personal allowance amounts
- National Insurance thresholds
- VAT threshold
- Corporation Tax rates
How to Never Miss a Deadline
Here’s a simple system that works:
Set Up Digital Reminders
Put every deadline that applies to your business in your calendar with these reminders:
- 2 weeks before the deadline
- 1 week before the deadline
- 2 days before the deadline
Don’t rely on memory. You’re busy running a business.
Keep Records as You Go
Don’t wait until deadline week to find receipts and invoices. Keep everything organized throughout the year.
Simple system:
- Use accounting software that tracks income and expenses automatically
- Scan or photograph receipts when you get them
- Reconcile your bank account weekly
- Run a profit and loss report monthly
When deadline time comes, everything is already there.
File Early When Possible
There’s no prize for filing on the deadline day. File early and you avoid:
- Technical problems with HMRC systems
- Last-minute panic
- Discovering you owe more than you thought with no time to prepare
I file my own tax return in May for the January deadline. No stress. No rush. Just done.
Get Professional Help
If tax deadlines stress you out or you’re not confident you’re doing things correctly, hire an accountant.
We charge fixed fees so you know exactly what it costs. Compare that to the cost of penalties, interest, and sleepless nights. Usually, an accountant pays for themselves.
What Happens If You Miss a Deadline
Don’t panic. Mistakes happen.
If you realize before the deadline: File immediately. Pay immediately if you owe money. You might still make it.
If you’ve already missed it:
- File or pay as soon as possible
- The longer you leave it, the worse the penalties
- Contact HMRC if you’re struggling to pay
- Explain if there’s a reasonable excuse (serious illness, bereavement, etc.)
HMRC can be surprisingly understanding if you communicate with them. They’re much less understanding if you ignore deadlines and hope the problem goes away.
Common Questions
“What if I can’t afford to pay my tax bill?”
Contact HMRC before the deadline. They offer Time to Pay arrangements where you can spread payments over several months. They’re much more likely to agree if you ask before you’re late.
“Do I need to file a tax return if I earned almost nothing?”
If you’re registered for Self-Assessment, yes. Even if you owe no tax, you still need to file. The £100 late filing penalty applies regardless of whether you owe money.
“Can I file my own tax return or do I need an accountant?”
You can file your own return if your tax affairs are simple. Many people do. But if you have multiple income sources, claim lots of expenses, or find it confusing, an accountant is worth it.
“What’s the earliest I can file my 2025/26 tax return?”
6 April 2026. HMRC opens the system the day after the tax year ends. You can file immediately if you have all your information ready.
Final Thoughts
Tax deadlines don’t need to be stressful. They’re predictable. They’re the same every year. The key is treating them like any other business task and building them into your routine.
Mark the relevant deadlines in your calendar right now. Set up your reminders. Keep your records organized throughout the year. File early when you can.
If you’re affected by Making Tax Digital for Income Tax, start preparing now. Get your software sorted. Learn how it works. Don’t wait until April 2026 to figure it out.
Do these things and you’ll never pay a penalty or lose sleep over a deadline again.
About the Author:
David Moore is the founder of Green & Moore Accountancy, a carbon-neutral accounting practice supporting purpose-driven small businesses across the UK. Green & Moore helps businesses stay on top of their tax obligations with clear, jargon-free guidance and fixed-fee pricing.
Need help with your taxes or Making Tax Digital? Book a free consultation to discuss how Green & Moore can take the stress out of tax deadlines.