Self Assessment Deadline January 2026: What to Do Now

The 31 January 2026 online filing and payment deadline for the 2024 to 2025 Self Assessment tax year has passed.

If you still have a 2024 to 2025 return or payment outstanding, the practical answer is simple: file and pay as soon as possible. HMRC says earlier tax-return deadlines have passed and you may have to pay a penalty, so delay can make the position worse.

If you are planning ahead, the next main Self Assessment online deadline is 31 January 2027 for the 2025 to 2026 tax year.

Quick Summary

• The 2024 to 2025 online return and payment deadline was 31 January 2026.
• If you missed it, send the return and pay what you can as soon as possible.
• HMRC charges separate penalties for late filing and late payment, plus interest on unpaid tax.
• The 2025 to 2026 return can be filed from 6 April 2026, with the online deadline on 31 January 2027.
• PAYE workers can still need Self Assessment if they have self-employment, property, investment, foreign, Child Benefit charge, or relief-claim issues outside payroll.

Key Dates Now

If You Missed the January 2026 Deadline

Do these first:

1. Send the outstanding return.
2. Pay what you owe, or as much as you can.
3. Check your HMRC account for penalties, interest, and any payments on account.
4. Contact HMRC if you cannot pay in full.

Filing late and paying late are separate issues. If you cannot pay everything today, sending the return still matters because late-filing penalties continue to build independently.

Who Needs to File Self Assessment?

HMRC says you must send a tax return if, in the last tax year, any of these applied:

• you were self-employed as a sole trader and earned more than £1,000 before deducting expenses
• you were a partner in a business partnership
• you had to pay Capital Gains Tax
• you had to pay the High Income Child Benefit Charge and did not pay it through PAYE
• you are an off-payroll worker repaying a student or postgraduate loan

You may also need to file if you have untaxed income, including:

• rental income
• tips or commission
• income from savings, investments, or dividends
• foreign income

PAYE handles most employee tax automatically, but PAYE does not make every tax issue disappear. If your salary is taxed through payroll but you also have side income, property income, capital gains, or a relief claim, use HMRC's checker before assuming you are outside Self Assessment.

Check if you need to send a tax return

First-Time Filer?

If you need to complete a 2025 to 2026 return and have not filed before, tell HMRC by 5 October 2026.

Register at gov.uk/register-for-self-assessment. HMRC will send your Unique Taxpayer Reference, usually by post, so leave time before the filing deadline.

If you register after 5 October 2026, HMRC says it will send a different filing deadline, usually 3 months from the date of its letter or email. The payment deadline is still 31 January 2027.

What Information Do You Need?

Gather the records that match your income sources:

• P60s and P45s from employment
• P11Ds for taxable benefits
• self-employment income and expense records
• rental income and property expense records
• bank interest and dividend records
• pension contribution statements
• Gift Aid and work-expense records
• capital gains records, including buy and sell dates
• your National Insurance number and UTR

If you are using estimates because records are missing, keep a note of why and update the return when accurate figures are available.

How to File Online

Go to gov.uk/log-in-file-self-assessment-tax-return and sign in with your Government Gateway details.

The online return asks for personal details, employment income, self-employment, property income, savings and dividends, pensions, reliefs, and capital gains where relevant. You can save progress and return later.

Before submitting:

• compare pre-filled information with your P60, payslips, bank records, and other evidence
• check that all income sources are included
• review the HMRC calculation
• save the submission receipt

Common Mistakes to Avoid

Leaving Out Income

Include all taxable income that belongs on the return, even if some tax has already been deducted. HMRC receives information from employers, banks, pension providers, and other sources, so omissions can be expensive.

Claiming Expenses Without Evidence

Self-employed and property expenses need a clear link to the business or rental activity. Keep receipts, invoices, statements, mileage records, and notes for any apportionment.

Missing Pension Relief

Some higher-rate pension relief is claimed through Self Assessment, depending on how the pension scheme gives relief. Check your pension statement and the return guidance before assuming payroll has dealt with it.

Read more about pension tax relief

Ignoring Payments on Account

If payments on account apply, your January payment can include a balancing payment for the previous year plus the first payment on account for the current year. The second payment on account is normally due on 31 July.

Penalties for Late Returns and Payments

HMRC charges late-filing penalties if you send a return late:

Late-payment penalties are separate. HMRC says penalties of 5% of the unpaid tax apply at 30 days, 6 months, and 12 months. Interest is also charged on unpaid tax.

The exact cost depends on your facts, so use HMRC's penalty estimator if you are already late.

Estimate your Self Assessment penalties

If You Cannot Pay in Full

Do not ignore the bill. HMRC says you can get help if you cannot pay on time, and you may be able to set up a payment plan, also known as a Time to Pay arrangement.

You can also make payments towards your bill before the deadline, including weekly or monthly payments, if you prefer.

Pay your Self Assessment tax bill

Paying Through Your PAYE Tax Code

If you already pay tax through PAYE, HMRC may be able to collect an eligible Self Assessment bill through your tax code.

The GOV.UK conditions include:

• the bill must be less than £3,000
• you must already pay tax through PAYE, such as from employment or a company pension
• you must submit a paper return by 31 October or an online return by 30 December

If you miss the 30 December online deadline, you will need to pay another way.

PAYE Workers With Side Income

This is the group PayeTax readers often miss.

Your payslip may be correct and you may still need Self Assessment because of income outside payroll. Examples include:

• freelance work alongside employment
• a rental property
• dividends or savings income that needs reporting
• capital gains
• High Income Child Benefit Charge issues
• pension or Gift Aid relief claims that are not handled automatically

Use PayeTax for the payroll side of the picture, then use HMRC or an adviser for the Self Assessment filing obligation.

• Calculate your PAYE take-home pay
• Review National Insurance deductions
• Read PayeTax's methodology and limitations

Planning for the 2025 to 2026 Return

The cleaner way to handle Self Assessment is to avoid January pressure:

1. Gather records from April onward.
2. Check whether you need to register by 5 October 2026.
3. File early if your records are ready.
4. Submit by 30 December 2026 if you want HMRC to consider collecting an eligible bill through your PAYE code.
5. Pay by 31 January 2027.

Filing early does not mean paying early. It gives you more time to check the calculation, budget for the bill, and fix problems before the deadline.

Frequently Asked Questions

What was the Self Assessment deadline for 2024 to 2025?

The online filing and payment deadline for the 2024 to 2025 Self Assessment tax year was 31 January 2026. Paper returns were due by 31 October 2025.

What is the next online Self Assessment deadline?

The next main online deadline is 31 January 2027 for the 2025 to 2026 tax year. HMRC must also receive payment by that date.

Can I still file after 31 January 2026?

Yes. If you missed the deadline, file as soon as possible. Late-filing penalties and late-payment consequences can increase over time.

Can I get an extension?

HMRC rarely treats Self Assessment deadlines as flexible. If you have a reasonable excuse, you may be able to appeal a penalty, but you should still file and pay as soon as possible.

Do PAYE-only employees need to file?

Most PAYE-only employees do not need Self Assessment if all income and reliefs are handled through payroll. You may still need to file if HMRC asks you to, or if you have untaxed income, capital gains, Child Benefit charge issues, or relief claims outside PAYE.

Key Takeaways

• The 31 January 2026 deadline for 2024 to 2025 has passed.
• If you missed it, file and pay as soon as possible.
• Late filing, late payment, and interest are separate costs.
• The next main online deadline is 31 January 2027 for 2025 to 2026.
• PAYE workers should check side income, property income, gains, and relief claims.
• PayeTax can help with PAYE calculations, but it does not file Self Assessment returns.

Official Sources Checked

• Self Assessment tax return deadlines
• Who must send a Self Assessment tax return
• Self Assessment penalties
• Pay your Self Assessment tax bill
• Register for Self Assessment

This article is for general information only. It is not tax advice or a substitute for HMRC guidance for your specific circumstances. Check GOV.UK or speak to a qualified tax adviser if you are unsure.