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| Covers Self Assessment, Corporation Tax, VAT, PAYE, MTD ITSA, and Companies House |
Don’t worry, if you miss a tax deadline, it doesn’t mean you’re a bad business owner. It typically indicates that you were not told there are six different deadlines, each with its own deadline and penalty, and that they are unrelated to one another.
This is the actual issue. Businesses in the UK do not miss deadlines as they are disorganisation. They miss it because the system is complicated and most guides cover only one aspect at a time. You complete your quarterly VAT return on time and feel you are compliant — only to get a penalty notice because your corporation tax was due 3 months before your CT600 was submitted — and nobody said that.
This guide addresses that. It brings together all HMRC and Companies House duties for 2026 – clear dates, clear penalties and a practical system with no missed steps.
2026 is more important than most years for UK HMRC tax deadlines. Making Tax Digital for Income Tax has now been rolled out for everyone earning more than £50,000 a year. CT600 fixed penalties doubled in April. Aside from compliance, HMRC’s late payment interest rate is 7.75% per annum, which is the real cost of unpaid tax. If you don’t already have a tax calendar for your business to check HMRC filing deadlines, then it’s time to create one.
The One Thing Most Guides Get Wrong
They treat each tax as a separate topic. In reality, your responsibilities overlap.
- The Corporation tax payment deadline is on 1st January.
- PAYE Due on the 19th/22nd of each month.
- Pay VAT return 7 May.
- The CT600 returns will be due 31 March, 2026 (three months after the payment).
Missed the payment in January whilst waiting for the accountant to draw up accounts in March, and HMRC has been applying 7.75% interest, which is daily throughout. No notification has been sent to you.
It is not a coincidence. This is what the system of things was set up to do.
Complete UK Tax Deadline Calendar 2026
May 2026 figures from HMRC gov.uk. The dates for paying CT600 and the corporation tax deadline in the UK differ depending on the accounting period end. Please check with a qualified accountant for your dates. Here is the UK tax deadlines calendar.
| Source: HMRC gov.uk, May 2026. CT600 and corporation tax payment dates vary by accounting period end. Verify with a qualified accountant for your specific dates. |
| Obligation | Deadline | Who It Applies To | Penalty Risk |
| Self Assessment (Paper) | 31 October, 2026 | Individuals, sole traders, directors | £100 automatic |
| Self Assessment — Online | 31 January 2027 (midnight) | Individuals, sole traders, directors | £100 + £10/day after 3 months |
| Balancing Payment (2025/26) | 31 January 2027 | Individuals, sole traders, directors | 7.75% p.a. interest from 1 Feb |
| 2nd Payment on Account | 31 July 2026 | Self-assessment taxpayers | Interest from 1 August |
| Corporation Tax Payment | 9 months + 1 day after period end | All limited companies (inc. dormant) | 7.75% p.a. daily interest |
| Companies House Accounts | 12 months after period end | UK limited companies | £200 day-one penalty |
| VAT Return — Q1 (Jan–Mar) | 7 May 2026 | VAT-registered businesses | £150–£1,500 fine |
| VAT Return — Q2 (Apr–Jun) | 7 August 2026 | VAT-registered businesses | Penalty points → £200 |
| VAT Return — Q3 (Jul–Sep) | 7 November 2026 | VAT-registered businesses | Penalty points accumulate |
| VAT Return — Q4 (Oct–Dec) | 7 February 2027 | VAT-registered businesses | 1–4% of late amount |
| PAYE & NIC — Electronic | 22nd of the following month | All UK employers | £300 per form, £60/day |
| PAYE & NIC — Postal | 19th of the following month | All UK employers | £300 per employee |
| P11D — Benefits in Kind | 6 July 2026 | Employers with benefits | Points-based penalty |
| P60 — Year-End Certificate | 31 May 2026 | All employers | Employer compliance action |
| MTD ITSA — Q1 Update | 5 August 2026 | Self-employed/landlords >£50k income | Points-based penalty |
| Capital Gains (Property) | 60 days from completion | Property sellers | Automatic penalty + interest |
Self Assessment 2026: Who Must File and What’s Actually Due
Do you need to file?
You must file a Self Assessment return for 2025/26 if you were any of the following:
Self-employed and earning more than £1,000 a year.
A director of a company, whether all the income is received through PAYE or not.
A landlord whose rental income is more than £2,500 a year.
A person who earns more than £100,000 a year.
A taxpayer whose investment income was more than or in addition to their regular income.
Subject to High Income Child Benefit Charge (income over £60,000)
If the foreign income is not taxed, it is considered to be in receipt of untaxed foreign income.
Not yet registered? The deadline to notify HMRC of your obligation for 2025/26 is 5 October 2026. Missing it adds a failure-to-notify penalty on top of any late filing penalty.
| → Register for Self Assessment: https://www.gov.uk/log-in-file-self-assessment-tax-return/register-if-youre-self-employed |
The January problem nobody explains
The 31 January 2027 is not a single deadline. It’s three all due at once:
- Make your online return for 2025/26.
- Pay your 2025/26 balancing payment
- Make the first instalment for 2026/27.
That’s the third one that trips people up. A sole trader owing £8,000 for 2025/26 also owes £4,000 as a first payment on account — a total January outgoing of £12,000. This cash demand cannot be reduced — both amounts are legally due on the same date.
Best practice: set aside 25–30% of net profit every month — not just in January.
Payments on account
Required when your Self Assessment bill exceeds more than £1,000 and if it gets less than 80% is collected through PAYE. Each payment is 50% of the previous year’s net liability.
- Second payment on account: It is on 31 July 2026
- If your income has fallen, apply to reduce payments on account proactively. If HMRC finds the reduction was excessive, interest applies retrospectively.
→ Reduce your payments on account: https://www.gov.uk/understand-self-assessment-bill/payments-on-account
Penalty structure — Self Assessment
| Trigger | Penalty |
| 1 Day Late | £100 automatic (even with no tax owed) |
| 3 Months Late | £10/day for up to 90 days (max £900) |
| 6 Months Late | 5% of outstanding tax or £300, whichever is higher |
| 12 Months Late | Further 5% or £300; deliberate cases up to 100% of tax due |
| Checklist: What to gather before filing |
Corporation Tax 2026: The Two-Deadline Trap
This is the single most expensive misunderstanding in UK business tax.
Corporation tax has two completely independent deadlines. Most directors treat them as one.
| Obligation | Formula | Example: 31 March 2025 Year-End |
| Payment | 9 months + 1 day after period end | 1 January |
| CT 600 Filing | 12 months after period end | 31 March 2026 |
| Company House Accounts | 9 months after year-end | 31 December 2025 |
You must pay three months before you file. This means you would need to estimate your liability based on draft accounts and pay it before the final numbers are ready.
What does this cost in practice?
A company has an end of year on 30 September 2025 and is due £35,000 corporation tax. The CT600 is due 30 September 2026. The payment closing date was 1st July 2026.
This is when the director awaits the accountant—accounts come out in August. By then, a month’s interest on £35,000 at 7.75% will have been about £234 – avoidable charges. The fact that the accounts are ‘nearly ready’ is irrelevant to HMRC.
CT600 penalties from April 2026
HMRC doubled fixed penalties for the first time since the late 1990s:
| Trigger | Penalty |
| Day 1 late | £200 (was £100) |
| 3 months late | Further £200 (total £400; repeat offenders up to £1,000) |
| 6 months late | 10% surcharge on unpaid tax |
| 12 months late | Further 10% Surcharge |
On a £50,000 liability, cumulative penalties can exceed £10,400 before interest. On a £0 liability: still £200 on day one.
The dormant company trap
Many directors believe that if their company is dormant, there is no CT600 liability. This is wrong.
A CT600 is a document that must be sent to HMRC by all UK limited companies, even those that have no income and no tax to pay. It takes only a few minutes to file a dormant CT600. Failure to file results in a £200 penalty on day one, with further penalties if it remains outstanding.
→ File a CT600 online: https://www.gov.uk/file-your-company-accounts-and-tax-return
Companies House vs HMRC — not the same filing
These are separate obligations, filed to separate portals, under separate penalty regimes:
- Companies House: Statutory annual accounts within 9 months of the year end→ https://www.gov.uk/file-your-confirmation-statement-with-companies-house
- HMRC: CT600 tax computation in iXBRL format, on time at the end of the year→ https://www.gov.uk/pay-corporation-tax
The Companies House filing deadline is different from HMRC; not filing one will not meet the other.
VAT Deadlines and MTD Compliance 2026
2026 quarterly deadlines
| Quarter | Period End | Submission Deadline |
| Q1 | 31 March 2026 | 7 May 2026 |
| Q2 | 30 June 2026 | 7 August 2026 |
| Q3 | 30 September 2026 | 7 November 2026 |
| Q4 | 31 December 2026 | 7 February 2027 |
Non-standard VAT periods (monthly, annual) have different dates. Check yours at: https://www.gov.uk/vat-returns/deadlines
The digital link rule — where most businesses fail
The Making Tax Digital VAT deadlines have been in place since 2022. Accounting software is not the only thing required.
MTD needs to be connected digitally from source to submission without interruption. No manual re-entry can be made at any stage.
✓ Compliant: Bank feeds are direct to your software → submitted via API
✓ Non Compliant: A report is downloaded, totals are then retyped into a spreadsheet and then uploaded again.
The manual re-entry clears the link. HMRC compliance reviews focus in particular on the integrity of the link throughout the process.
→ Check your MTD for VAT status: https://www.gov.uk/guidance/make-sure-you-have-compatible-software-for-making-tax-digital-for-vat
Penalty points — how they stack up
| Filer Type | Points Before Financial Penalty |
| Annual Filers | 2 points |
| Quarterly Filers | 4 points |
| Monthly Filers | 5 points |
One point is added for every late return. For every repeat late submission after the initial: £200 per late submission until a clean compliance period has been reached, which resets the counter. A quarterly filer is three late returns away from being subject to continued fines.
Common VAT errors that trigger HMRC notices
- Input VAT for block entertainment
- Using the incorrect application rate on a supply
- Manually entering the digital link
- Failing to register after exceeding the £90,000 threshold
- Failure to properly manage VAT accounting for imports (post-Brexit).
- Unsuccessfully allocating partial exemption apportionment
The last two are often the basis for full compliance enquiries, rather than penalties.
Making Tax Digital for Income Tax (MTD ITSA) — Live from April 2026
Who is in scope right now
MTD ITSA will be compulsory for anyone with combined self-employment and property income over £50,000 on their 2024/25 Self Assessment return from 6 April 2026.
The annual return is substituted with:
- 4 quarterly updates (income & expenses) sent electronically.
- An end-of-period statement
- A final declaration
They must be submitted via the software that HMRC has approved. The Portal does not work with HMRC.
→ Find compatible MTD ITSA software: https://www.gov.uk/guidance/find-software-thats-compatible-with-making-tax-digital-for-income-tax
2026 quarterly update deadlines
| Quarter | Period | Deadline |
| Q1 | April-June 2026 | 5 August 2026 |
| Q2 | July-September 2026 | 5 November 2026 |
| Q3 | October- December 2026 | 5 February 2027 |
| Q4 | January- March 2027 | 5 May 2027 |
If your qualifying income was above £50,000 on your 2024/25 return and you have not started quarterly submissions, you are already late. The Q1 deadline was 5 August 2026. Seek advice from a qualified accountant immediately.
Upcoming threshold changes
| Date | Income Threshold |
| April 2026(Now) | £50,000 |
| April 2027 | £30,000 |
| April 2028 | £20,000 |
HMRC estimates 42% of all self-employed UK taxpayers will be within MTD by 2028.
The Hidden Costs: Interest, Non-Deductibility, and Director Liability
Daily interest — no notification sent
HMRC charges 7.75% per annum from the day after your deadline. No warning letter. No grace period.
| Amount Outstanding | Daily Charge | After 90 Days |
| £10,000 | £2.12/day | ~£191 |
| £50,000 | £10.62/day | ~£955 |
| £100,000 | £21.23/day | ~£1,911 |
You won’t know the total until you’ve paid in full and HMRC has issued the interest notice with payment confirmation.
Penalties are never tax-deductible
All HMRC penalties (file, payment, surcharge, and daily) are specifically disallowed as a business expense. There is no cost saving because a penalty fee of £500 is charged to your business, and you need to pay £500.
Director’s personal liability
The powers of the Finance Act allow HMRC to seek the director’s personal liability in cases of deliberate non-compliance and in cases where the company has been wound up, for example, with outstanding tax liabilities where HMRC could have known that were due.
New enforcement powers post-2020 have seen directors of companies in administration or liquidation investigated for personal recovery action when companies have not had PAYE running.
What compounding looks like in practice
A sole trader with a combined income of £65,000:
- Misses MTD ITSA Q1 submission: -1 point
- Misses Q2 → 2 points
- Late returns of VAT more than three days: 1 point
- Late balancing payment of £12,000 in January → ~£100 in HMRC interest
None of these are tax-deductible. Every one of them could have been prevented with a UK tax deadlines calendar and a standing order.
How to Build a Tax Calendar That Actually Works
Those businesses that always follow uk tax deadlines and manage to avoid penalties are not necessarily more organised than others. They have improved infrastructure.
1. Map every obligation on 6 April.
Make a list of all the tax deadlines for the next year. Give them a name: give one a named person for each. Tasks are forgotten if no one is assigned to them.
2. Set two alerts: 30 days and 7 days before every deadline.
The 30-day warning activates preparations. It takes 7 days to be alerted, so everything should be ready to submit. If it’s not at 7 days, then it’s a problem, not a deadline.
3. Close your books monthly, not quarterly.
Monthly reconciliation is not a problem anymore: VAT returns are hours long. This will keep your estimate of corporation tax up to date. You don’t panic and stop filing.
4. Separate the CT600 payment and filing into two calendar events.
They’re not the same deadline. There is no connection between them. Mark them in isolation, using a different preparation step.
5. Use MTD-compatible software as your single source of truth.
Xero, QuickBooks, Sage, and FreeAgent all maintain digital links natively. Manual re-entry is the fastest route to a compliance failure.
→ HMRC list of approved MTD software: https://www.gov.uk/guidance/sign-up-your-business-for-making-tax-digital-for-income-tax
6. File six weeks early. Pay on time.
The deadline is NOT a target date; it is a safety net. Errors can be corrected for the CT600 early correction. VAT paid two weeks late, at the end of the quarter, is never technical but financial.
How serious accountants actually work: There’s no deadline on the deadline day. 6 to 8 weeks early for returns to CT600. Self-assessments are submitted in October, if possible. VAT returns are filed within 2 weeks of the end of each quarter. When you have a deadline to meet, there is the possibility of a penalty if there are disruptions. When it’s your safety net, things are kept manageable. Enter all obligations on 6 April.
What to Do If You Cannot Pay on Time
Contact HMRC in advance of the deadline, not after.
Time to Pay (TTP) arrangements enable eligible taxpayers to spread liabilities over time. If your debt is under £30,000, then you can apply for a Self Assessment debt online, instead of calling HMRC within the 60-day period.
Interest continues to run throughout TTP. However, penalty payments can be suspended during the arrangement period — a much better deal than paying the penalty.
→ Set up a Time to Pay arrangement: https://www.gov.uk/difficulties-paying-hmrc
→ Self Assessment TTP (under £30k): https://www.gov.uk/pay-self-assessment-tax-bill/pay-in-instalments(online) Contact HMRC before the deadline — not after.
Can You Appeal an HMRC Penalty?
Yes — but on very restricted grounds.
Accepted: Serious illness or bereavement, or genuine failure of the HMRC system at the time of submission, are considered as a good cause.
Not accepted: using a third party (accountant/Bookkeeper), if unaware of the deadline, busy, or cash flow issues.
Appeals must be made in writing within 30 days of the penalty notice and in support of the appeal.
→ Appeal a Self Assessment penalty: https://www.gov.uk/appeal-tax-penalty
Frequently Asked Questions
Q: 1 What is the Self Assessment filing deadline for 2025/26?
Paper: 31 October 2026. Online: 31st January at midnight 2027. Tax owed (balance to be paid plus first payment on account) is also due 31 January 2027.
Q2: When is corporation tax due for a 31 March 2025 year-end?
The payment was due on 1 January 2026. CT600 filing deadline was due 31 March 2026. They’re all independent — timely payments do not equal timely filing.
Q3: What are the CT600 penalties in 2026?
£200 on day one (from 20th April 2026) and again in three months, capped at £200 at six months and 10% at twelve months if tax is not paid. Affects dormant companies with no tax liability.
Q4: Does MTD ITSA apply to me?
Yes — If the total of all your self-employment and property income is over £50,000 on your 2024/25 return, it will be after 6 April 2026. The deadline for Q1 was 5 August 2026. If you haven’t started, get help right away.
Q5: What is HMRC’s late payment interest rate?
7.75% APR (as of January 2026), paid daily. On £50,000 outstanding, that is £10.62 per day.
Q6: Do I need to file a CT600 if my company is dormant?
Yes. HMRC needs to receive a CT600 from every limited company in the UK, including dormant companies with no income and no tax to pay. The penalty for not filing is £200 from day one.
Q7: What VAT rate applies to my business?
Standard rate: 20%. Reduced rate: 5%. There are categories of zero-rated and exempted supplies — refer to the type of your supply at: https://www.gov.uk/guidance/rates-of-vat-on-different-goods-and-services
Key HMRC and Companies House URLs for 2026
| Task | URL |
| File Self Assessment online | https://www.gov.uk/log-in-file-self-assessment-tax-return |
| Pay Self Assessment | https://www.gov.uk/pay-self-assessment-tax-bill |
| Register for Self Assessment | https://www.gov.uk/register-for-self-assessment |
| Pay corporation tax | https://www.gov.uk/pay-corporation-tax |
| File CT600 and Companies House accounts | https://www.gov.uk/file-your-company-accounts-and-tax-return |
| File Companies House accounts separately | https://www.gov.uk/file-your-confirmation-statement-with-companies-house |
| VAT return deadlines | https://www.gov.uk/vat-returns/deadlines |
| MTD for VAT | https://www.gov.uk/guidance/making-tax-digital-for-vat |
| MTD ITSA software | https://www.gov.uk/guidance/find-software-thats-compatible-with-making-tax-digital-for-income-tax |
| Appeal a penalty | https://www.gov.uk/appeal-tax-penalty |
| Time to Pay arrangement | https://www.gov.uk/difficulties-paying-hmrc |
| PAYE and payroll | https://www.gov.uk/running-payroll |
| P11D filing | https://www.gov.uk/employer-reporting-expenses-benefits |
| Capital Gains Tax | https://www.gov.uk/report-and-pay-your-capital-gains-tax |
Sources: Companies House, HMRC gov.uk (May 2026), and CT600 fines advice (April 2026 update). A trained accountant should always confirm deadlines that are dependent on your accounting period.
