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Self Assessment Tax Return: An Introduction

Self Assessment Tax Returns: An Introduction

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Self Assessment Tax Returns: Jack Ross Guide

Understanding Self Assessment Tax Returns

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The Self-Assessment Tax Return is a system HMRC uses to collect income tax from those who are not paid via a PAYE system from an employer. Tax is usually deducted automatically from wages, pensions, and savings. However, people and businesses with income that is not PAYE must report it in a self-assessment tax return.

Who Needs to Fill in a Self Assessment Tax Return?

If you are self-employed, a business partner, or a limited company director, you probably need to fill in a self-assessment tax return. You also need to complete a tax return if you have income from renting out a property, savings, investments, or income from overseas.

Key Components of the Self Assessment Tax Return

Your self-assessment tax return will include details about your income, any capital gains, and claimable allowances and reliefs. It will encompass various forms of income, including but not limited to earnings from employment, benefits, pensions, and capital gains.

When to Register for Self Assessment

If this is your first time doing so, you need to register separately for self-assessment with HMRC. The registration deadline is typically the 5th October following the end of the tax year for which you need to file.

Deadlines: A Crucial Element

The tax year in the UK runs from 6th April to the following 5th April. You must send your tax return by the deadline of 31st January following the end of the tax year. If you opt for a paper tax return, the deadline is earlier, typically 31st October following the end of the tax year. Missing the deadline could result in a penalty.

How Much Tax Do You Owe?

Once you have submitted your self-assessment tax return, HMRC will calculate the tax you owe based on the information provided. This includes income tax, national insurance contributions, and capital gains tax, among other deductions.

Paying Your Tax Bill

You need to pay your self-assessment tax bill by the 31st January deadline. Sometimes, you may be required to make an additional “payment on account” toward your next tax bill. Your tax bill will detail this if it is necessary.

Why You Might Receive a Tax Refund

In some cases, you may find that you have paid too much tax in the previous tax year. In these instances, you might be eligible for a tax refund. You can claim tax back by amending your tax return or contacting HMRC.

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Preparing for Self Assessment Tax Returns

Get Organised Early

The process of filling in your self-assessment tax return may seem daunting, especially if it is your first time. However, a bit of preparation can go a long way. The more organised you are, the smoother the process will be.

Gather All Necessary Documents

Before you start to fill in a self-assessment form, ensure you have all the required documents. These can include P60s, P45s, bank statements, and receipts for expenses. It is also advisable to keep records of any charitable donations, as these can be claimed for tax relief.

Determine Your Taxable Income

Your taxable income includes money earned from employment, self-employment, rental income, and any capital gains. You will also need to account for any other income, such as dividends from shares, interest on savings, and benefits. Once you have a complete picture, you can start filling in your self-assessment tax return.

Claim Allowances and Reliefs

Various allowances and reliefs can reduce your tax bill. These can range from personal allowances to tax relief on pension contributions. If you have incurred any business expenses during the tax year, you may also be able to deduct these from your taxable income.

How to Complete a Tax Return

To complete a tax return, you can either do it online via the website or by filling out a paper return. Online returns are often more convenient and offer the benefit of automatic calculations. Plus, you have until 31st January following the end of the tax year to submit it, giving you extra time compared to paper returns, which are due by the end of October.

Paying Your Self Assessment Tax

Once you have completed your self-assessment, you will receive a tax bill from HMRC. This will include not just the tax due but may also require a ‘payment on account’ for the next tax year. Payments are typically due by 31st January following the tax year you are paying for.

Penalties for Missed Deadlines

Failure to meet the 31st January deadline can result in penalties. The initial fixed penalty is £100, and further charges apply if the delay continues. It is crucial to contact HMRC as soon as possible if you believe you will miss the deadline.

Get Professional Advice

If you find the self-assessment process challenging or have complex tax situations, it might be beneficial to seek professional advice. Specialist tax advisors like Jack Ross Chartered Accountants can help ensure you pay the right amount of tax and claim all the reliefs you are entitled to. Use the contact form on the right, and one of our team will be in touch. 


Filling in a self-assessment tax return involves several steps, from gathering necessary documents to understanding your taxable income and liaising with HMRC. While the process may seem complex, understanding the basics can make the task far less daunting. Remember, when in doubt, consult HMRC or seek professional advice.

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A self-assessment tax return is a form used to declare your income and calculate how much tax you owe for the past tax year.

To complete your self-assessment form, you must first register with HMRC and enter your National Insurance number. You will then need to enter details about any income and other financial information relating to the tax year that you are declaring, such as any benefits or expenses. Once filled in, submit your return via the online system or by post.

If you fail to pay your self assessment tax by the due date, penalties and interest may be added onto any outstanding balance. You may also be prosecuted for non-payment if it is deemed necessary.

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