Posted March 24, 2025

The Complete Beginner’s Guide to Filing Your First Tax Return

Filing your first tax return can feel like navigating uncharted territory. Whether you’ve recently become self-employed, started earning additional income, or received a notice from HMRC, understanding the basics of the Self-Assessment process is essential for compliance and peace of mind. This guide will walk you through everything you need to know to confidently complete your first tax return.

Do I Need to File a Tax Return?

Before diving into the how-to, let’s confirm whether you actually need to file a tax return. You’ll typically need to complete a Self-Assessment tax return if:

You’re self-employed and earned more than £1,000 in the tax year
You’re a partner in a business partnership
You received untaxed income such as rental income or tips
You earned income from investments, dividends, or savings over certain thresholds
You need to claim tax relief or make voluntary Class 2 National Insurance contributions
You have income from abroad that needs to be taxed
You’re a high earner (over £100,000) or need to pay the High-Income Child Benefit Charge

If you’re unsure, HMRC’s online checker tool can help determine your filing requirements, or you can contact us for a personalised assessment.

Key Deadlines to Remember

For the current tax year (2024/2025), these are the critical dates:

5 October 2025: Deadline to register for Self-Assessment if you’re newly self-employed or have new income to report
31 October 2025: Deadline for paper tax returns (if you choose not to file online)
31 January 2026: Deadline for online tax returns and paying any tax owed
31 July 2025: Deadline for making your second payment on account (if applicable)

Missing these deadlines can result in penalties, so mark them in your calendar well in advance.

Getting Started: Registration

If this is your first time filing, you’ll need to register for Self-Assessment:

Visit the HMRC website and select “Register for Self-Assessment”
Choose the option that best describes your situation (usually “self-employed” or “not self-employed”)
Complete the registration process, which will require personal details including your National Insurance number
Wait to receive your Unique Taxpayer Reference (UTR) by post (this can take up to 10 working days)
Once you have your UTR, activate your account for online services and set up your Government Gateway ID

Don’t leave registration until the last minute—this process takes time, and you’ll need your UTR to file.

Gathering Your Documentation

Preparation is key to a smooth filing experience. Collect the following before you begin:

Personal information: Your National Insurance number, UTR, and details of any previous tax references
Employment records: P60 (end of year statement) and P45 (if you left a job during the tax year)
Self-employment records: Business income, expenses, receipts, and bank statements
Property income: Records of rental income and allowable expenses
Investment information: Dividend statements, interest certificates, and records of any asset disposals
Pension statements: Details of contributions and any income received
Charitable donations: Records of Gift Aid donations
Student loan information: Statements of any repayments made or outstanding balances

Creating a dedicated folder (physical or digital) for these documents will save you significant time and stress.

How to Complete Your Tax Return: Step by Step

Log in to your HMRC online account using your Government Gateway ID
Select “Complete tax return” for the relevant tax year
Work through each relevant section, answering all questions honestly and accurately
Save your progress regularly as you go—the system times out after 15 minutes of inactivity
Review all figures carefully before submission—simple errors can lead to compliance issues
Submit your completed return and make note of your submission reference

The online system will calculate your tax liability automatically once all information is entered.

Making Payment

After submitting your return, you’ll be informed of:

The total tax due for the year
Any payments on account required for the next tax year
Details of how to make payment

Payment options include:

Bank transfer
Debit card payment online
Direct Debit
Payment at your bank or building society
Payment by cheque (though this is increasingly discouraged)

Remember to allow sufficient time for your payment to reach HMRC, particularly if using slower methods.

Common First-Timer Mistakes to Avoid

Leaving registration too late: The registration process takes time, and delay can result in missing the filing deadline
Claiming expenses without evidence: Ensure you have receipts or records for all business expenses claimed
Forgetting about payments on account: These advance payments toward your next tax bill can take you by surprise
Missing deadlines: Set reminders well in advance of key dates
Assuming PAYE income doesn’t need reporting: If you have both employment and self-employment income, you need to report both
Overlooking tax-deductible expenses: Many legitimate business costs can reduce your tax bill
DIY when you’re not confident: Getting professional help often saves money in the long run

How We Can Help

While this guide covers the basics, tax returns can quickly become complex depending on your situation. Our experienced team can:

Help determine if you need to file a return
Guide you through the registration process
Advise on allowable expenses and potential tax savings
Review your financial records and complete your return accurately
Represent you in communications with HMRC
Provide year-round tax planning advice to minimise future liabilities

Filing your first tax return doesn’t have to be intimidating. With proper preparation and the right support, you can navigate this process confidently and efficiently. Contact us today for a no-obligation consultation about your Self-Assessment needs.

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