What happens if I miss the tax return deadline?

You'll receive an automatic £100 penalty immediately, even if you have no tax to pay. Further penalties apply after 3 months, 6 months, and 12 months. Interest is also charged on any unpaid tax.

When do I need to register for self assessment?

You must register by 5th October following the tax year in which you need to complete a return. For 2025/26, register by 5th October 2026. First-time self-employed? Register as soon as you start.

When do I have to pay my tax bill?

Any tax owed for the previous tax year must be paid by 31st January. If you make payments on account, you'll also have a payment due on 31st July. The balancing payment is due the following 31st January.

When is the Tax Return Deadline? UK Self Assessment Dates 2026

Q: When is the tax return deadline?

The deadline for online self assessment tax returns is 31st January following the tax year. For the 2024/25 tax year, the deadline is 31st January 2026. Paper returns have an earlier deadline of 31st October.

Knowing your tax deadlines helps you avoid penalties and plan your finances. Here are all the key dates you need to know for self assessment in 2026.

Key Deadlines: 2024/25 Tax Year

Date	Deadline
5 April 2025	2024/25 tax year ends
5 October 2025	Register for self assessment (new filers)
31 October 2025	Paper tax return deadline
30 December 2025	Online deadline for PAYE collection (under £3,000)
31 January 2026	Online tax return deadline
31 January 2026	Pay tax owed for 2024/25
31 January 2026	First payment on account for 2025/26
31 July 2026	Second payment on account for 2025/26

Key Deadlines: 2025/26 Tax Year

Date	Deadline
6 April 2025	2025/26 tax year begins
5 April 2026	2025/26 tax year ends
5 October 2026	Register for self assessment (new filers)
31 October 2026	Paper tax return deadline
30 December 2026	Online deadline for PAYE collection (under £3,000)
31 January 2027	Online tax return deadline
31 January 2027	Pay tax owed for 2025/26

Who Needs to File a Tax Return

You Must File If You:

Situation	Tax Return Required
Self-employed income over £1,000	Yes
Partner in a business partnership	Yes
Untaxed income over £2,500	Yes
Income from property/rentals	Yes
Annual income over £150,000	Yes
Foreign income needing declaring	Yes
Capital gains over CGT allowance	Yes
High Income Child Benefit Charge	Yes
Director of a company	Usually yes
HMRC sends you a notice to file	Yes

You May Need to File If You:

Situation	Details
Employed with other income	Side hustle, investments
Claiming certain reliefs	Some require tax return claim
Non-UK income	Employment or investments abroad

Registration Deadline

First Time Filing?

Tax Year	Register By
2024/25	5 October 2025
2025/26	5 October 2026

How to Register

Go to gov.uk/register-for-self-assessment
Choose your registration type (self-employed, partnership, etc.)
Complete online form
Receive UTR (Unique Taxpayer Reference) by post (allow 10 days)
Activate online account

Don’t delay: Even if you miss the October deadline, register immediately to minimise issues.

Paper vs Online Returns

Paper Return

Feature	Details
Deadline	31 October
How to request	Download from HMRC or call
Calculation	HMRC calculates your tax
Submission	Post to HMRC
Receipt	Limited confirmation

Online Return

Feature	Details
Deadline	31 January
How to file	HMRC online, or approved software
Calculation	Instant
Submission	Electronic
Receipt	Immediate confirmation

Recommendation: Always file online — more time, instant calculation, easier amendments.

Payment Deadlines

Balancing Payment

What	When
Any tax owed for previous year	31 January
Includes	Income tax, National Insurance, student loan

Payments on Account

If your tax bill was over £1,000 (and less than 80% was collected through PAYE), you may need to make advance payments:

Payment	Date	Amount
First payment on account	31 January	50% of previous year’s bill
Second payment on account	31 July	50% of previous year’s bill
Balancing payment	Following 31 January	Any remainder owed

Example: Payments on Account

Scenario	Amount
2024/25 tax bill	£5,000
First payment on account (Jan 2026)	£2,500
Second payment on account (July 2026)	£2,500
2025/26 actual bill	£6,000
Already paid via payments on account	£5,000
Balancing payment (Jan 2027)	£1,000
Plus new payments on account	£3,000 (50% of £6,000)

What Happens If You Miss the Deadline

Filing Penalties

Delay	Penalty
1 day late	£100 (immediate)
3 months late	£10 per day (up to £900)
6 months late	£300 or 5% of tax (whichever higher)
12 months late	£300 or 5% of tax (whichever higher)

Maximum: Up to £1,600 in penalties + any amount based on tax owed.

Payment Penalties

Delay	Penalty
30 days late	5% of tax owed
6 months late	Additional 5%
12 months late	Additional 5%
Plus interest	Currently ~7.75% (changes)

Example: Late Filing and Payment

Situation	Cost
Tax owed	£3,000
Filed 4 months late	£100 + £100 (3m+) = £200 penalty
Paid 7 months late	5% + 5% = £300 penalty
Interest (~7.5% for 7 months)	~£130
Total penalties & interest	~£630

Reasonable Excuse

Penalties can be appealed if you had a reasonable excuse:

May Be Accepted	Unlikely to Be Accepted
Serious illness	Pressure of work
Bereavement of close relative	Lack of funds
Computer failure (last minute)	Ignorance of deadline
HMRC error	Trusted someone else
Fire/flood affecting records	Didn’t receive reminder

Special Circumstances

PAYE Collection (Under £3,000)

Feature	Details
Deadline	30 December
What it does	Tax collected through PAYE code
Benefit	Spread payment over following year
Eligibility	Tax owed under £3,000

File by 30 December to have small amounts (under £3,000) collected through your tax code.

Budget Payment Plan

Feature	Details
What	HMRC plan to spread payments
When to set up	Before 31 January
How	Through HMRC online account
Payments	Weekly or monthly

Time to Pay Arrangement

If you can’t pay by the deadline:

Contact HMRC before deadline
Call Self Assessment helpline
Propose payment plan
May avoid late payment penalties

Calendar Summary

January

Date	Action
1-30 January	Final push to complete return
31 January	ONLINE DEADLINE
31 January	PAYMENT DEADLINE
31 January	First payment on account

April

Date	Action
5 April	Tax year ends
6 April	New tax year begins

July

Date	Action
31 July	Second payment on account

October

Date	Action
5 October	Register for self assessment
31 October	Paper return deadline

December

Date	Action
30 December	PAYE collection deadline

Tips to Avoid Deadline Stress

Tip	Benefit
File in April/May	Maximum time for corrections
Keep records throughout year	Less scrambling
Use accounting software	Automates calculations
Set calendar reminders	Multiple alerts
Put aside tax monthly	Avoid January shock
Check HMRC messages	They notify of issues

Useful Contacts

Service	Contact
Self Assessment helpline	0300 200 3310
HMRC online services	gov.uk/log-in-register-hmrc-online-services
Agent authorization	For accountants
Payment problems	Contact HMRC before deadline

Summary

Key Deadline	Date
Register for self assessment	5 October
Paper return	31 October
PAYE collection	30 December
Online return	31 January
Pay tax owed	31 January
Second payment on account	31 July