Smart Ways to Know If You Need to File a Self Assessment in the UK (2025/26)

How to Know If You Must File a Self Assessment in the UK (2025/26)

Filing your Self Assessment tax return with HMRC is essential if you earn untaxed income in the UK. Whether you’re self-employed, a landlord, or a company director, knowing your obligations can save you from costly fines — such as the £100 HMRC penalty for late Self Assessment tax returns starting January 2025.

At Tax Return Assist, our expert accountants make the process of filing your Self Assessment simple, accurate, and stress-free.

self assessment

What Is a Self Assessment Tax Return?

A Self Assessment tax return is how HMRC collects Income Tax from individuals and businesses whose tax isn’t automatically deducted through PAYE.

You’ll need to register for Self Assessment if you receive income that HMRC doesn’t already tax — for example:

• Earnings from self-employment or freelancing

• Rental income from property

• Dividends or investment income

• Foreign income

• Tips or commissions

• High income (over £100,000 annually)

• Pension or savings income not taxed at source

Visit our Self Assessment service page for full support on registration and filing.

Who Needs to File a Self Assessment for 2025/26?

You must file a Self Assessment tax return if you fall into any of these categories:

1. Self-employed individuals or sole traders earning more than £1,000

   • Get help from our Sole Trader Accountants

2. Company directors or contractors earning dividends or outside IR35

   • Check our Contractor Accountants

3. Small business owners or landlords

   • Explore our Small Business Accountants

4. People with multiple income sources (e.g. PAYE + side business)

5. Individuals earning foreign income

When and How to Register for Self Assessment

You must register for Self Assessment by 5 October 2025 if you’re required to file for the 2024/25 tax year.

You can register for Self Assessment online via the HMRC website. After registering, you’ll receive a Unique Taxpayer Reference (UTR) — your Self Assessment number — used to log in and file your return.

If you need assistance registering, our team can handle the entire setup — including HMRC registration, UTR retrieval, and tax filing — on your behalf. Please contact Instant Quotes

Key Deadlines for Self Assessment (2025/26)

Missing any of these deadlines can lead to penalties — starting at £100 for late filing, as HMRC recently announced:

“HMRC to fine UK households £100 for late Self Assessment tax returns starting January 2025.”

Avoid these penalties by filing early with help from our Tax Return experts.

How to File Your Self Assessment Tax Return Online

You can file your Self Assessment tax return online via HMRC. The process involves:

1. Signing into your HMRC login or Government Gateway account

2. Entering your income, expenses, and tax reliefs

3. Submitting your Self Assessment tax return form

4. Paying any tax due

If this sounds complicated — don’t worry. Our accountants at Tax Return Assist will handle everything for you.

Avoid HMRC Penalties and Mistakes

Common Self Assessment mistakes include:

• Forgetting to register on time

• Using the wrong UTR number

• Missing expenses or claiming ineligible ones

• Not paying tax by 31 January

Each mistake can result in interest charges or penalties. Work with our specialists to ensure full HMRC compliance and accuracy.

 How Tax Return Assist Can Help

At Tax Return Assist, we offer:

• Complete Self Assessment tax return filing

• Bookkeeping and record management

• VAT returns and small business accounting

• Support for sole traders, contractors, and limited companies

We’re here to simplify tax season so you can focus on running your business.

✅ Ready to File Your Self Assessment?

Don’t wait until January! File your 2025/26 Self Assessment today with our expert team.
Visit 👉 https://taxreturnassist.co.uk/self-assessment/