Self Assessment Tax Return 2025

Filing a Self Assessment Tax Return can sound confusing, but it’s actually quite simple once you understand the process. In the UK, this is how you tell HMRC (Her Majesty’s Revenue and Customs) how much money you earned and how much tax you owe.

If you are self-employed, a freelancer, or earn income outside your regular job, you’ll likely need to submit a self assessment tax return. The year 2025 brings a few updates to how tax returns are filed, especially with the Making Tax Digital (MTD) system, which is slowly becoming the new standard for online submissions.

In this guide, you’ll learn who needs to file, what documents you need, and how to complete your tax return online — all in simple steps.

Who Needs to File a Self Assessment Tax Return?

Not everyone in the UK needs to file a tax return. It mostly applies to people who earn money that isn’t already taxed through PAYE (Pay As You Earn). You need to file a Self Assessment Tax Return if you are:

• Self-employed or run your own small business.
• A freelancer or contractor earning money from clients.
• A landlord earning rent from property.
• An investor making money from dividends or interest.
• A company director receiving income outside of a salary.
• Someone with an income above £100,000.

If you’re unsure, HMRC’s online checker can help you find out whether you need to file one or not. But in general, if your income is not automatically taxed, you’ll need to do a self assessment tax return.

Key Deadlines for the 2025 Tax Year

Knowing your tax return deadlines is important. Missing them can lead to penalties and stress — something we all want to avoid!

Here are the main dates for 2025:

• Paper returns: Deadline is 31 October 2025.
• Online returns: Deadline is 31 January 2026.
• Tax payment: You must pay any owed tax by 31 January 2026.

If you miss these dates, HMRC can charge you a late filing penalty, starting at £100 and increasing the longer you delay. So, always aim to file your self assessment tax return early.

Documents You’ll Need Before Filing

Before you start your online tax filing, gather all the right documents. This will make the process smooth and quick. You’ll need:

• Income records (invoices, salary slips, bank statements).
• Business expense receipts (office supplies, travel, utilities).
• P60 or P45 forms (for employed individuals).
• P11D forms (if you received company benefits).
• Unique Taxpayer Reference (UTR) number.

Having these ready will help you avoid mistakes and make sure you include all your taxable income and allowable business expenses.

How to File Your Self Assessment Tax Return

Filing your self assessment tax return online is now the easiest and most popular way to do it. Here’s a step-by-step guide:

1. Register with HMRC: If you’re filing for the first time, register for self assessment and get your UTR number.
2. Log in to your HMRC account: Visit the HMRC website and sign in using your Government Gateway ID.
3. Complete your online tax form: Enter your income, expenses, and other details carefully.
4. Check your calculation: The system will automatically calculate how much tax you owe.
5. Submit your return: Once done, click submit before the deadline.
6. Pay your tax bill: You can pay online, through bank transfer, or by setting up a direct debit.

If you prefer, you can still send a paper form, but it must arrive before 31 October.

Common Mistakes to Avoid When Filing

Even simple mistakes can cause problems with your self assessment return. Here are a few things to avoid:

• Missing the deadline — this leads to automatic penalties.
• Entering wrong figures — always double-check your numbers.
• Forgetting to claim expenses — things like phone bills, internet, or travel costs may be allowable deductions.
• Not keeping records — HMRC may ask for proof later.
• Ignoring your tax payments — even if you filed on time, you must also pay by the deadline.

Being careful helps you avoid extra charges and keeps your tax filing stress-free.

Tax Deductions and Allowances You Should Know

Many people pay more tax than they should because they don’t know what they can claim. Here are some tax reliefs and allowances you should look into:

• Personal allowance: The amount you can earn before paying tax.
• Business expenses: Office rent, travel, internet, and tools used for work.
• Charitable donations: Can sometimes reduce your taxable income.
• Home office deductions: If you work from home, part of your bills may count as expenses.

Claiming these properly can help reduce your tax bill and make your self assessment tax return more accurate.

How to Pay Your Tax Bill

Once HMRC confirms how much you owe, you’ll need to pay your self assessment tax bill. There are several ways to pay:

• Online payment through your HMRC account.
• Bank transfer or Direct Debit.
• Debit or credit card payments.

If you can’t pay on time, don’t panic. You can contact HMRC and set up a payment plan to spread the cost. But don’t ignore it — unpaid tax can lead to interest charges or penalties.

Updates and Changes for the 2025 Tax Year

Every year, tax rules can change slightly. For the 2025 tax year, a few updates include:

• Digital filing is becoming standard under the Making Tax Digital (MTD) system.
• Some tax thresholds and allowances have been adjusted.
• Online filing systems have improved for quicker submission.

Always check the latest information on your HMRC online account before submitting your return.

Professional Help: When to Hire a Tax Advisor or Accountant

If doing your self assessment tax return feels stressful, you can always get help from a tax advisor or accountant. They can:

• Make sure your return is accurate.
• Help you find tax reliefs you might miss.
• Handle complex cases like property income or multiple jobs.

Hiring a professional might cost a little, but it can save you time and possibly reduce your overall tax bill.

Be Prepared and File Early

Filing your Self Assessment Tax Return 2025 doesn’t have to be difficult. The key is to stay organized, gather your documents early, and submit your online tax return before the deadline.

By understanding your income, expenses, and deadlines, you can avoid penalties and file with confidence. If you start now, you’ll have plenty of time to check everything carefully and even get your tax refund faster if you’re due one.

Remember, tax season doesn’t have to be stressful — just stay informed, plan ahead, and file early!