Self Assessment Tax Return Dates UK — Key Deadlines

Missing Self Assessment deadlines can be expensive. Here are all the key dates you need to know.

Key Deadlines

2024/25 Tax Year

Date	Deadline
6 April 2024	Tax year starts
5 April 2025	Tax year ends
5 October 2025	Register for Self Assessment
31 October 2025	Paper return deadline
30 December 2025	Pay via PAYE (if eligible)
31 January 2026	Online return + payment deadline

2025/26 Tax Year

Date	Deadline
6 April 2025	Tax year starts
5 April 2026	Tax year ends
5 October 2026	Register for Self Assessment
31 October 2026	Paper return deadline
30 December 2026	Pay via PAYE (if eligible)
31 January 2027	Online return + payment deadline

Registration Deadlines

When to Register

Your Situation	Register By
Self-employed from 2024/25	5 October 2025
Self-employed from 2025/26	5 October 2026
New income source	5 October after tax year
Company director	5 October after tax year

Who Must Register

Reason	Self Assessment Needed
Self-employed	Yes
Partner in partnership	Yes
Company director	Usually
Rental income	Yes (if above thresholds)
Capital gains	Yes (over annual exemption)
High income (£150k+)	Yes
Child Benefit (high income)	Yes (if earning £60k+)
Foreign income	Yes

How to Register

Method	Process
Online	Create Government Gateway
Time taken	10-20 days for UTR
Keep safe	Your UTR number

Filing Deadlines

Paper Returns

Deadline	Details
31 October	Following tax year end
Example	31 October 2025 for 2024/25
HMRC calculates	Tax for you
Must post	In time to arrive

Online Returns

Deadline	Details
31 January	Following tax year end
Example	31 January 2026 for 2024/25
You calculate	Or software does
3 months extra	vs paper

Which to Choose

Method	Best For
Paper	Simple affairs
Online	Most people
Software	Complex returns
Accountant	Peace of mind

Payment Deadlines

Balancing Payment

When Due	31 January
Amount	Tax owed for year
Plus	First payment on account (if applicable)
Method	Online, phone, bank

Payments on Account

What They Are	Advance payments
First payment	31 January
Second payment	31 July
Each payment	50% of previous year’s bill
Final balance	Following 31 January

Payment on Account Example

Element	Date	Amount
2024/25 tax	31 Jan 2026	£3,000
1st payment on account	31 Jan 2026	£1,500
2nd payment on account	31 July 2026	£1,500
2025/26 balance	31 Jan 2027	Varies

Can Reduce Payments on Account

If You Expect	Action
Lower tax bill	Apply to reduce
Form SA303	Or claim online
Be accurate	Penalties if underestimate

Late Filing Penalties

Penalty Timeline

How Late	Penalty
1 day late	£100
3 months late	£10/day (max £900)
6 months late	5% of tax or £300 (higher)
12 months late	Another 5% or £300 (higher)

Example Penalty Calculation

Scenario	£2,000 Tax Owed
1 day late	£100
3 months late	£100 + £900 = £1,000
6 months late	£1,000 + £300 = £1,300
12 months late	£1,300 + £300 = £1,600

Appeals

Reason	May Be Accepted
Bereavement	Close family
Serious illness	Hospitalisation
HMRC error	Their mistake
Natural disaster	Fire, flood
IT failure	HMRC’s system

Late Payment Penalties

Payment Penalties

How Late	Penalty
30 days	First 5% of tax
6 months	Another 5%
12 months	Another 5%

Interest

On Late Payment	Current Rate
Charged from	Due date
Rate	Bank rate + 2.5%
Compounds	Adds to debt

Example: Late Payment

Scenario	£5,000 Tax Owed
Due	31 January
Paid	1 August (6 months late)
30-day penalty	£250
6-month penalty	£250
Interest (~3.5%)	~£87
Total extra	~£587

PAYE Coding Option

Pay Through Tax Code

Eligibility	Criteria
Amount	Under £3,000
Submit return	By 30 December
Already in PAYE	For other income
HMRC allows	Not guaranteed

How It Works

Process	Details
Return by 30 Dec	Online
Tax code adjusted	Following year
Paid gradually	Through salary
No lump sum	Easier budgeting

Budget Payment Plan

If You Can’t Pay

Option	Details
Time to Pay	Arrangement with HMRC
Up to 12 months	Sometimes longer
Interest charged	Still applies
Set up online	If under £30k

Setting Up

Method	Process
Online	Self-serve if eligible
Phone	Call HMRC helpline
After deadline	Can still arrange
Stops enforcement	Usually

Planning Calendar

Annual Cycle

Month	Action
April	New tax year starts, begin records
October	Register if new, paper deadline
December	Aim to file online
January	Final deadline, pay
July	2nd payment on account

Best Practice

Approach	Benefit
File early	Peace of mind
Know bill	Plan payment
Pay on time	Avoid penalties
Keep records	For 5 years

Summary

Key Deadline	Date
Register	5 October after tax year
Paper return	31 October
Online return	31 January
Payment	31 January
2nd payment on account	31 July

Penalties	Cost
1 day late filing	£100
3 months late	Up to £1,000
Late payment 30 days	5% of tax
Late payment 6 months	Extra 5%

Checklist	Status
Registered (if needed)	□
UTR received	□
Records ready	□
Return filed	□
Payment made	□