Reasonable Excuse for Late Tax Return: UK Tax Deadlines, Penalties and HMRC Appeals

Missing a tax deadline does not always mean you have to accept an HMRC penalty. If circumstances genuinely prevented you from filing a tax return or paying tax on time, you may have a reasonable excuse for a late tax return or late tax payment.

HMRC considers reasonable excuse claims based on the individual circumstances. Examples can include serious illness, an unexpected hospital stay, bereavement, fire or flood, theft, certain computer or software failures, HMRC online service problems and other unexpected events outside your control. However, you normally need to act without unreasonable delay once the problem is resolved.

This guide explains the main UK tax deadlines, what can happen if you miss each one, what HMRC may consider a reasonable excuse, and how to challenge a penalty.

Quick answer: A reasonable excuse is a genuine circumstance that prevented you from meeting a tax obligation despite taking reasonable care. It is not an automatic exemption. HMRC looks at the facts of each case, including what happened, how long it lasted and how quickly you acted afterwards.

Key UK Tax Deadlines at a Glance

The exact deadline that applies to you depends on the tax, your circumstances and sometimes your accounting period. The following table covers the major deadlines that individuals, landlords, self-employed people, employers and companies commonly need to know.

These are the principal deadlines covered in this guide, rather than every deadline under the UK tax system. Specialist taxes and individual circumstances can have different filing and payment dates.

What Is a Reasonable Excuse for a Late Tax Return?

A reasonable excuse for a late tax return is a circumstance that genuinely prevented you from meeting your tax obligation on time.

HMRC does not operate a simple checklist where every excuse is automatically accepted. Instead, it considers the facts and circumstances of the individual case. GOV.UK gives examples including serious illness, an unexpected hospital stay, bereavement, computer or software failure, HMRC online service problems, fire, flood, theft and certain unexpected postal problems.

The key question is generally whether something outside your control prevented you from complying, despite taking reasonable care.

Just as importantly, you should put things right as soon as you are able to. Continuing to delay after the problem has ended can weaken a reasonable excuse claim.

Examples of circumstances that may qualify

A reasonable excuse may include:

• Serious or life-threatening illness
• An unexpected hospital stay
• The death of a partner or close relative shortly before the deadline
• Fire, flood or theft
• Unexpected computer or software failure while preparing an online return
• Problems with HMRC’s online services
• Unpredictable postal delays
• Certain circumstances connected with a disability or mental illness
• An unexpected event outside your control
• Losing essential records because of circumstances outside your control

HMRC’s examples are guidance rather than an exhaustive list. Whether an excuse is accepted depends on the facts.

What normally does not count as a reasonable excuse?

Some explanations are unlikely to be accepted on their own, including:

• Forgetting the tax deadline
• Not receiving an HMRC reminder
• Finding the HMRC online system difficult to use
• Making a mistake on the return
• Not having enough money to pay a tax bill
• Simply relying on another person to deal with your tax affairs where you did not take reasonable care

For example, HMRC guidance specifically states that insufficient funds are generally not a reasonable excuse unless the lack of funds resulted from events outside the taxpayer’s control.

Self Assessment Tax Return Deadlines and Reasonable Excuses

Self Assessment is the deadline most people mean when they search for reasonable excuse for late tax return or reasonable excuse HMRC late filing.

For the 2025/26 tax year, the main Self Assessment deadlines are:

• 5 October 2026 – deadline to register for Self Assessment for the 2025/26 tax year where registration is required
• 30 December 2026 – deadline if you want HMRC to collect certain tax through your PAYE tax code
• 31 October 2026 – deadline for a paper tax return
• 31 January 2027 – deadline for an online tax return
• 31 January 2027 – deadline for the balancing payment and, where applicable, the first payment on account
• 31 July 2027 – deadline for the second payment on account

If you want to reduce the pressure around the January deadline, filing your tax return early can give you more time to identify errors, arrange payment and deal with unexpected issues. HMRC confirms that the paper return deadline is 31 October 2026 and the online return deadline for the 2025/26 tax year is 31 January 2027.

1. Missing the Self Assessment Paper Return Deadline

The paper Self Assessment deadline is normally 31 October following the end of the relevant tax year.

If you miss it, HMRC can issue a late filing penalty.

What is a reasonable excuse for a late paper tax return?

The same general reasonable-excuse principles can apply. For example, you may have a case if:

• You suffered a serious illness around the deadline.
• You were unexpectedly admitted to hospital.
• A close family member died shortly before the deadline.
• Fire, flood or theft destroyed essential tax records.
• An unexpected event outside your control prevented you from completing the return.

You should complete the return as soon as possible once the circumstances preventing you from filing have ended.

2. Missing the Online Self Assessment Deadline

For most taxpayers filing online, the deadline is 31 January.

For example, the online return for the 2025/26 tax year must normally be submitted by 11:59pm on 31 January 2027.

What happens if your Self Assessment return is late?

The standard late filing penalties can include:

• £100 initial penalty
• £10 per day after three months, up to a maximum of £900
• A further penalty after six months of 5% of the tax due or £300, whichever is greater
• Another 5% or £300 penalty after 12 months, whichever is greater

Higher penalties can apply in cases involving deliberate withholding of information.

Importantly, the initial £100 penalty can apply even if you have no tax to pay or have already paid the tax due.

Can you appeal a late Self Assessment penalty?

Yes. If you had a genuine reasonable excuse, you can appeal the penalty.

Your explanation should make clear:

1. What happened
2. When it happened
3. How it prevented you from filing
4. Why you could not reasonably meet the deadline
5. When the problem ended
6. How quickly you filed after it ended
7. What evidence you have

3. Missing the Self Assessment Tax Payment Deadline

Filing your tax return and paying your tax are separate obligations.

For Self Assessment, the main payment deadline is normally 31 January. If you have payments on account, the second payment is normally due on 31 July.

What happens if you pay Self Assessment tax late?

HMRC can charge:

• A late payment penalty of 5% of the tax unpaid at 30 days
• A further 5% at six months
• Another 5% at 12 months
• Interest on the overdue tax

HMRC’s current guidance confirms the 5% penalties at 30 days, six months and 12 months, as well as interest on unpaid tax.

What is a reasonable excuse for late payment of tax?

A reasonable excuse for late payment of tax can be relevant where circumstances outside your control genuinely prevented you from paying.

Examples may include:

• Serious illness
• Unexpected hospitalisation
• Bereavement
• A serious unexpected event affecting your ability to deal with your tax affairs
• Certain technical or HMRC service problems where they genuinely prevented payment
• Other exceptional circumstances outside your control

However, simply saying that you did not have enough money will generally not be enough. HMRC specifically states that insufficient funds are not normally a reasonable excuse unless they resulted from events outside your control.

If the problem ends before the penalty trigger point, you should make arrangements to pay rather than simply waiting.

4. Missing a Self Assessment Payment on Account

Payments on account are normally due:

• 31 January
• 31 July

Each payment is normally half of the previous year’s tax bill, subject to the rules for who needs to make payments on account.

What if you miss a payment on account?

Late payment consequences can arise, and interest may accrue.

If an unexpected event prevented you from paying, explain precisely what happened and why it prevented payment.

A useful reasonable-excuse explanation should not simply say:

“I could not afford to pay.”

Instead, explain the exceptional circumstance that caused the financial difficulty, when it occurred and what you did once you were able to resolve the situation.

5. Missing the Self Assessment Registration Deadline

If you need to register for Self Assessment, the deadline is generally 5 October following the end of the tax year in which you first had a tax liability requiring registration.

Failing to register can potentially lead to a failure-to-notify penalty, particularly where tax remains unpaid. HMRC confirms that a person who registers late and does not pay all tax due by 31 January may receive a failure-to-notify penalty.

A reasonable excuse may be relevant depending on the circumstances, but registration obligations can involve rules that differ from ordinary late-return penalties.

6. Missing the 30 December Self Assessment Deadline

If you want HMRC to collect certain Self Assessment tax through your PAYE tax code, the online return generally needs to be submitted by 30 December.

This is not the main Self Assessment filing deadline. If you miss it, you may simply need to pay the tax another way.

Therefore, missing 30 December does not automatically mean you have submitted your tax return late if you subsequently meet the 31 January filing deadline.

VAT Return Deadlines and Reasonable Excuse

VAT deadlines work differently from Self Assessment. For most VAT-registered businesses, VAT Returns are submitted every three months. The online filing and payment deadline is usually one calendar month and seven days after the end of the accounting period.

For example, if a VAT accounting period ends on 31 March, the normal deadline will be 7 May. Keeping VAT records organised throughout the accounting period can make deadlines easier to manage, and cloud bookkeeping can make quarterly VAT returns less painful.

What happens if a VAT Return is late?

For VAT accounting periods beginning on or after 1 January 2023, late VAT Return submissions operate under a penalty-point system.

Each late return generally results in a penalty point. Once the relevant threshold is reached, a £200 penalty can apply, with further £200 penalties for subsequent late submissions while at the threshold. The threshold depends on whether returns are annual, quarterly or monthly.

Can you claim a reasonable excuse for a late VAT Return?

Yes. HMRC’s VAT guidance confirms that a penalty point or financial penalty does not arise where the taxpayer satisfies HMRC, or a tribunal on appeal, that they had a reasonable excuse.

The general principles are similar:

• The event must genuinely prevent compliance.
• You should have taken reasonable care.
• You should remedy the failure without unreasonable delay.
• Lack of funds is generally not enough unless caused by circumstances outside your control.

Late VAT Payment: What Does It Cost?

VAT late payment penalties are separate from late submission penalties for periods beginning on or after 1 January 2023.

If payment is:

• Up to 15 days late: no late payment penalty
• 16-30 days late: first penalty calculated at 3% of the VAT outstanding at day 15
• 31 days or more late: the first penalty can include 3% of the day-15 amount plus 3% of the amount outstanding at day 30
• A second penalty can then accrue at a daily rate of 10% per year on the outstanding amount

Late payment interest is also charged from the first day the payment is overdue.

A reasonable excuse can be relevant when challenging a late VAT payment penalty, although interest is treated differently. HMRC states that late payment interest itself cannot generally be appealed simply because there was a reasonable excuse; objections are available in specific circumstances such as an HMRC error or certain disputes over the relevant payment date.

Corporation Tax Deadlines and Reasonable Excuse

Companies have two important Corporation Tax deadlines. Companies should also consider whether any Corporation Tax reliefs and allowances are available when calculating their overall tax liability.

Corporation Tax payment deadline

Corporation Tax is normally due nine months and one day after the end of the accounting period. For example, if a company’s accounting period ends on 31 March 2026, Corporation Tax would normally be due on 1 January 2027.

Meeting filing deadlines is only one part of managing a company’s tax position; proactive tax planning strategies for companies can also help businesses prepare for their liabilities.

Company Tax Return deadline

The Company Tax Return is generally due 12 months after the end of the accounting period.

These are separate obligations. A company can therefore file its Corporation Tax Return on time but pay its Corporation Tax late, or vice versa.

Corporation Tax late filing penalties

If a Company Tax Return is late:

• 1 day late: £200
• 3 months late: another £200
• 6 months late: 10% of unpaid tax
• 12 months late: another 10% of unpaid tax

The £200 penalties can increase to £1,000 each if the company files late three times in a row.

Can a company claim a reasonable excuse?

Yes. HMRC allows an appeal against a Corporation Tax late filing penalty where there is a reasonable excuse.

A company should explain why the return could not be filed on time and should file the outstanding return before appealing the penalty.

HMRC’s internal guidance recognises that unforeseen misfortune can constitute a reasonable excuse where a company made every reasonable effort to meet its obligations and remedied the failure as soon as reasonably possible.

PAYE Deadlines for Employers

Employers normally need to pay PAYE and National Insurance deductions to HMRC by:

• 22nd of the following tax month when paying electronically
• 19th where paying by cheque

Quarterly PAYE payers generally have until the 22nd after the end of the relevant quarter for electronic payments. Employers dealing with employee benefits and expenses should also understand whether PAYE Settlement Agreements may be relevant to their reporting and tax obligations.

What happens if PAYE is paid late?

PAYE late-payment penalties can depend on the number of defaults and how late the payment is.

For monthly and quarterly PAYE payments, penalty percentages can range from 1% to 4% depending on the number of defaults. Additional 5% penalties can apply where amounts remain unpaid after six and 12 months. Interest also continues to accrue on unpaid amounts.

If an unexpected event prevented an employer from complying, the circumstances should be explained to HMRC and any available reasonable-excuse provisions considered.

Construction Industry Scheme (CIS) Deadlines

CIS contractors generally need to submit their monthly CIS return by the 19th of the following month. Staying on top of CIS contractors’ monthly tax chores can help reduce the risk of missing the 19th-of-the-month reporting deadline.

For example, a return covering 6 May to 5 June must reach HMRC by 19 June.

CIS late filing penalties

The standard penalties can include:

• £100 for being one day late
• £200 after two months
• £300 or 5% of CIS deductions after six months, whichever is higher
• A further £300 or 5% after 12 months, whichever is higher
• Potential additional penalties for very late returns

HMRC confirms that a CIS penalty can be appealed within 30 days of the penalty notice.

If a genuine reasonable excuse caused the delay, explain the circumstances and provide evidence where possible.

Capital Gains Tax Deadline for UK Property

Capital Gains Tax has a particularly important deadline if you sell a UK residential property. Where the rules require a report, you normally have 60 days from completion to report the disposal and pay the Capital Gains Tax due.

This is much earlier than the normal Self Assessment timetable. Contractors should also ensure deductions are calculated correctly, so it is worth reviewing how CIS deduction rates are calculated alongside the monthly filing requirements.

What happens if you miss the 60-day deadline?

HMRC may charge interest and a penalty if the report and payment are late.

If an unexpected event genuinely prevented you from meeting the deadline, a reasonable excuse may be relevant to a penalty appeal.

For example, an unexpected hospitalisation or a serious event that prevented you from dealing with the property disposal reporting requirement could be relevant, depending on the facts.

Stamp Duty Land Tax Deadline

For transactions subject to Stamp Duty Land Tax in England and Northern Ireland, the SDLT return and any duty due generally need to be submitted and paid within 14 days of the effective transaction date.

If you miss the deadline, you may have to pay a late filing penalty and interest.

HMRC’s updated 2026 guidance confirms that late SDLT returns can attract fixed penalties and late payments can attract interest.

If circumstances outside your control prevented compliance, consider whether a reasonable-excuse argument is available.

Inheritance Tax Deadline

Inheritance Tax is subject to different rules from Self Assessment. Normally, any Inheritance Tax due must be paid by the end of the sixth month after the person’s death.

Executors and families should also consider whether current Inheritance Tax gift reliefs could affect the wider IHT position when reviewing an estate.

For example, where someone dies in January, the normal payment deadline is 31 July.

HMRC charges interest if Inheritance Tax is not paid by the due date. Because IHT involves estates and often complex administration, executors should obtain appropriate professional advice if a deadline has already been missed.

Does Late Tax Payment Increase the Amount of Tax You Owe?

Yes, potentially.

Late payment does not normally change the original tax liability itself. Instead, HMRC can add interest and penalties to the amount you owe.

The overall cost therefore depends on:

• The type of tax
• How much tax remains unpaid
• How late the payment is
• The applicable penalty regime
• The applicable HMRC interest rate
• Whether a reasonable excuse or other relief applies

For the main taxes covered by HMRC’s published interest table, the late-payment interest rate was 7.75% from 9 January 2026. HMRC sets its late-payment rate by reference to the Bank of England base rate, with the rate generally being base rate plus 4% under the current rules. Interest rates can change, so taxpayers should check the current HMRC rate when calculating a liability.

Example

Suppose you owe £10,000 and pay it late.

You may have to pay:

Original tax: £10,000
+ late payment interest: calculated for the period the tax remains outstanding
+ applicable late payment penalties: depending on the tax and how long payment is overdue

This means delaying payment can make the total amount you eventually have to pay significantly higher.

Late Tax Return vs Late Tax Payment: What Is the Difference?

These are often confused, but they are separate issues.

Late tax return

You have failed to submit the required return by the filing deadline.

For Self Assessment, this can lead to:

• £100 initial penalty
• Daily penalties after three months
• Further penalties after six months
• Further penalties after 12 months

Late tax payment

You submitted the return but did not pay the tax by the payment deadline.

This can lead to:

• Late payment penalties
• Interest on the unpaid tax

You can therefore have a late return, a late payment, or both.

What Evidence Can Support a Reasonable Excuse?

A reasonable-excuse appeal is stronger when you can demonstrate what happened rather than simply making a general statement.

Depending on the circumstances, useful evidence could include:

• Hospital or medical documentation
• Death or bereavement documentation
• Insurance or police records following theft
• Evidence of fire or flood
• Computer repair or technical support records
• Screenshots or records showing HMRC service problems
• Relevant correspondence with HMRC
• Postal evidence
• Evidence showing when the problem started and ended
• Records showing that you filed or paid promptly after the problem was resolved

You should keep records of important tax correspondence and problems that affect your ability to comply.

How to Appeal an HMRC Penalty for a Reasonable Excuse

If HMRC has issued a penalty and you believe you had a genuine reasonable excuse, you can normally appeal. Your appeal should be factual and specific. 

Clear and accurate information is important when dealing with HMRC, particularly as HMRC may identify suspicious or unusual tax returns for further attention.

Step 1: Identify the penalty

Check:

• Which tax the penalty relates to
• The relevant tax period
• The missed deadline
• The penalty amount
• The date on the penalty notice

Step 2: Explain what happened

State exactly what prevented you from filing or paying.

Avoid vague explanations such as:

“I had personal problems.”

Instead, explain the circumstances, when they happened and how they directly prevented you from meeting the deadline.

Step 3: Explain why you could not comply

This is particularly important.

The issue is not simply whether something difficult happened. You need to explain why that circumstance prevented you from meeting the particular tax obligation.

Step 4: Explain what you did afterwards

Tell HMRC when the problem ended and when you submitted the return or made payment.

HMRC’s guidance makes clear that taxpayers should take action without unreasonable delay once they are able to do so.

Step 5: Provide evidence

Where evidence exists, include it.

Step 6: Appeal promptly

GOV.UK states that tax penalty appeals are generally subject to a 30-day deadline from the date the penalty was issued, although the precise process can vary by tax and penalty.

For Self Assessment, HMRC’s internal guidance refers to the statutory appeal period as 30 days plus the relevant extension for the notice, so taxpayers should follow the deadline and instructions shown on their penalty notice.

What If HMRC Rejects Your Reasonable Excuse?

A rejected reasonable-excuse claim does not necessarily mean you have no further options.

Depending on the tax and penalty, you may be able to request an HMRC review or appeal to the tax tribunal.

If you have received a penalty, read the penalty notice carefully because it should explain how to challenge the decision and the applicable deadline.

If you disagree with the penalty, it can also be sensible to obtain professional advice, particularly where the penalty is substantial or the circumstances are complicated.

How to Write a Strong Reasonable Excuse for HMRC

A useful appeal should be concise, chronological and evidence-based.

A simple structure is:

1. The deadline:
State the tax obligation and deadline you missed.

2. The event:
Explain the unexpected circumstance.

3. The impact:
Explain precisely how the circumstance prevented you from filing or paying.

4. The duration:
State when the problem started and ended.

5. The corrective action:
Explain when you filed the return or paid the tax after the problem ended.

6. Evidence:
List or provide supporting evidence.

7. Request:
Ask HMRC to cancel or reconsider the penalty because you believe the circumstances amounted to a reasonable excuse.

The strongest explanation is usually one that allows HMRC to understand the entire timeline without having to guess what happened.

What Should You Do If You Have Already Missed a Tax Deadline?

Do not wait for HMRC to contact you.

The best course of action is usually:

1. File the outstanding return as soon as possible.
2. Pay as much of the tax as you can.
3. Contact HMRC if you cannot pay the full amount.
4. Identify whether you have a genuine reasonable excuse.
5. Collect evidence supporting the circumstances.
6. Appeal any penalty promptly if appropriate.
7. Keep records of your communications and evidence.

Acting quickly after a missed deadline is important because HMRC’s reasonable-excuse rules take into account whether the taxpayer remedied the failure without unreasonable delay. Taking action early can reduce the risk of further penalties and give you more time to resolve any issues, which is one reason filing your tax return early can make sense.

Final Checklist: Missed a Tax Deadline?

If you have missed a UK tax deadline, ask yourself:

• What tax deadline did I miss?
• Was the return late, the payment late, or both?
• What exactly prevented me from complying?
• Was the event unexpected or outside my control?
• Did I take reasonable care before the deadline?
• When did the problem start?
• When did it end?
• How quickly did I file or pay afterwards?
• What evidence can I provide?
• Has HMRC already issued a penalty?
• What is the appeal deadline on the penalty notice?
• Could interest or additional penalties continue to accrue?

If you can answer these questions clearly, you will have a much better basis for deciding whether a reasonable excuse for late tax return or reasonable excuse for late payment of tax may apply.

Conclusion

A missed tax deadline does not automatically mean that an HMRC penalty is unavoidable.

The important distinction is between simply being late and having a genuine reasonable excuse for being late. HMRC considers the facts of each case and may accept circumstances such as serious illness, bereavement, unexpected events, certain technical failures, HMRC service problems, fire, flood or theft.

However, taxpayers should not rely on a reasonable-excuse argument as a substitute for meeting deadlines. If a problem occurs, take action as soon as possible, file the return, pay what you can, contact HMRC where necessary and keep evidence of what happened.

The financial consequences of late payment can also build quickly because HMRC may charge both penalties and interest. The applicable rates and penalty rules depend on the tax involved and can change over time.

If you have received an HMRC penalty and believe circumstances outside your control prevented you from meeting the deadline, getting the facts and evidence together promptly can help you make a stronger appeal.

CASE STUDY: Helping a Taxpayer Appeal an HMRC Late Filing Penalty

A taxpayer contacted our Farringdon office, received an HMRC penalty after submitting their Self Assessment tax return after the filing deadline. The taxpayer had experienced an unexpected hospital stay around the deadline and was unable to access the records and information needed to complete the return.

Once they had recovered, the taxpayer submitted the outstanding return promptly but was concerned about the £100 late filing penalty and whether additional penalties could arise if the delay continued.

Cigma Accounting reviewed the timeline in detail, including the original filing deadline, the period of hospitalisation, when the taxpayer regained the ability to deal with their tax affairs and when the return was ultimately submitted. The circumstances were assessed against HMRC’s reasonable-excuse principles rather than simply relying on the fact that the taxpayer had been unwell.

Supporting evidence relating to the hospital stay was gathered, and the appeal clearly explained how the unexpected event prevented the taxpayer from complying with the deadline. It also demonstrated that the taxpayer acted without unreasonable delay once the circumstances had been resolved.

The structured appeal gave HMRC a clear chronology and supporting evidence for considering whether the penalty should be cancelled. The experience also highlighted the importance of acting quickly after a missed deadline and retaining evidence when circumstances outside a taxpayer’s control affect their ability to meet a tax obligation.