Self Assessment Guide

How to file a Self Assessment tax return online:

A step-by-step guide

Are you preparing to file your tax return online before the Self Assessment deadline of 31 January? Does the process feel overwhelming, especially if you’re new to Self Assessment or unsure where to begin?

While some individuals file their tax returns as early as the first day of the new tax year, it’s okay if you’re not one of them. Filing online is the easiest and most efficient method, offering benefits like avoiding postal delays and giving you more time to meet the deadline.

Though the idea of filing online might seem intimidating—especially if you’re not tech-savvy—proper preparation can make it simpler than you think. Tackling it sooner rather than later can also prevent last-minute stress.

This guide will walk you through tips for completing your Self Assessment tax return online. It covers key topics such as important deadlines, penalties, allowable expenses.

Please note that this guide does not provide legal or professional advice. If you’re unsure about anything, please contact us for specialized assistance.

So, is filing a tax return online easy? The answer is yes—let’s get started.

This guide will cover the following:

WHO needs to file a tax return?

For employees and pensioners, taxes are typically deducted automatically at source from wages and pensions through the PAYE system.

However, individuals and businesses with additional income not taxed at source—such as rental income, dividends, or freelance earnings—must report it via a Self Assessment tax return if the income exceeds a certain threshold.

If you were self-employed as a sole trader during the last tax year (6 April 2023 to 5 April 2024) and earned more than £1,000, you are required to file a tax return. This also applies if you took on freelance work or a side hustle alongside a full-time job, and your combined income exceeded the annual tax-free allowance of £12,570.

You must also file a return if you:

Were a partner in a business partnership.
Were a director of a limited company with untaxed income.
Earned more than £100,000 through PAYE.
Received untaxed income from sources like:

Rental properties.
Tips or commissions.
Savings, investments, or dividends.
Foreign income.

You may also file a return to claim income tax relief or prove self-employment status for benefits like Tax-Free Childcare or maternity allowance.

To check if you need to file, HMRC provides a decision tree tool.

Remember to register for Self Assessment by 5 October following the tax year you are declaring for. For the 2024–2025 tax year, the registration deadline is 5 October 2025.

Being informed and prepared can help you meet your obligations smoothly and avoid penalties.

Important dates and deadlines for Self Assessment

If you’ve registered for Self Assessment by the 5 October 2024 deadline for the 2023/24 tax year, there are several important dates to keep in mind:

Paper Tax Returns Deadline:
Submit paper tax returns by midnight on 31 October 2024.
Online Tax Returns Deadline:
File online tax returns by midnight on 31 January 2025.

Payments on Account

After filing your first tax return, you may need to make payments on account—advance payments towards your tax bill for the current tax year.

This applies if your last tax bill exceeded £1,000 or if less than 80% of your tax was already deducted at source (e.g., through PAYE). Payments are made in two instalments:

First Payment: Due by 31 January.
Second Payment: Due by 31 July.

Example Scenario

If Sarah owes £3,000 for her 2023/24 tax year, her total payment by 31 January 2025 would be £4,500. This includes:

£3,000 for the previous year’s tax.
£1,500 as the first instalment for her 2024/25 tax bill (50% of her expected total bill).

By 31 July 2025, she will need to pay the second instalment of £1,500.

If her income changes significantly in the following tax year, her payments on account will be adjusted accordingly in her next tax return.

By staying organized and aware of these deadlines, you can avoid penalties and manage your tax obligations more efficiently.

How to register and file a tax return online

For the 2022/23 tax year, 96% of tax returns were filed online, highlighting the convenience of this method. HMRC emphasizes that filing online is simple, secure, accessible 24/7, and allows you to sign up for email alerts and online messages for easier tax management.

Getting Started

If you’re new to filing online, you’ll need to register for an HMRC online account. Upon registration, HMRC will send you an activation code by post, which can take up to 10 working days in the UK or up to 21 days if you’re overseas. Along with the code, you’ll receive a Unique Taxpayer Reference (UTR) and a user ID.

If you’ve filed before but skipped the previous year, you’ll need to re-register for Self Assessment.

Before registering or completing the return, gather all the required information, including:

UTR and National Insurance number
Employer reference (if applicable)
Documents like your P60, P11D, P45, payslips, or P2 PAYE coding notice
Bank statements, profit/loss accounts (if self-employed), and other business records

Completing the Tax Return

The form is divided into several sections:

Personal Details: Start with your basic information.
Income Sources: Declare all sources of income, such as employment, self-employment, rental income, dividends, pensions, or overseas earnings. Answer “Yes” to relevant boxes to provide further details.
Additional Information: Declare items like student loans, charitable donations, pension contributions, or child benefit.

Ensure you report all income, even if you’re filing as a sole trader, as HMRC requires a complete overview. Use HMRC’s guide or supplementary pages for clarification if needed, and don’t send supporting documents unless requested by HMRC.

Filing Tips

Save your progress as you fill out the return—you can revisit and make changes before submission.
Double-check all figures before hitting submit.
Print a copy of your final return and the receipt for your records.

If there are major differences compared to previous returns, use the Further Information section to explain these changes.

Record-Keeping

You must retain all records used to complete your Self Assessment for at least five years after the 31 January filing deadline. This includes accounts and supporting documents. Failing to maintain adequate records may result in significant penalties if reviewed by HMRC.

By staying organized and carefully completing your return, you can navigate the process with confidence.

Claiming allowable expenses

If you’re self-employed, your business will have various operating costs. Many of these can be deducted as allowable expenses to calculate your taxable profit, provided they meet HMRC’s criteria. Common examples include:

Office-related costs: Such as stationery, phone bills, or internet.
Work-specific clothing: Uniforms or protective gear (note: regular clothing, including business suits, is not claimable).
Staff expenses: Salaries, wages, or subcontractor payments.
Financial charges: Insurance, bank charges, or business-related interest.
Professional fees: Some accountant or legal fees.
Business premises costs: Heating, lighting, and business rates, but not rent for a home office unless it’s exclusively used for work.
Advertising and marketing: Website development or promotional campaigns (excluding client entertainment).

Key Considerations for Tax Deductions

While HMRC’s online system calculates your tax liability, it doesn’t verify the accuracy of your figures or ensure you’ve claimed all eligible reliefs and allowances.

Common areas for tax relief, including:

Research and Development (R&D) expenditures.
Use of home as an office (within specified limits).
Capital allowances: Including full relief on eligible equipment under the Annual Investment Allowance (AIA).
Travel and accommodation when working away from home.

Simplified Expenses and the Trading Allowance

Instead of itemizing expenses, you might opt for simplified expenses, a flat-rate system covering costs like vehicle use, home office expenses, and business premises used as living spaces. While it saves time, it may reduce the total amount you can claim.

Alternatively, the government offers a £1,000 tax-free trading allowance for sole traders. However, if you claim this allowance, you cannot deduct additional expenses or capital allowances.

By understanding these options and carefully tracking expenses, you can maximize your tax savings while staying compliant with HMRC regulations.

Charitable donations and tax relief

Individual donations to charities or community amateur sports clubs (CASCs) are eligible for tax relief, so be sure to include all your charitable contributions in your tax return.

The way tax relief is applied depends on how you donate:

Gift Aid: The charity claims basic-rate tax relief directly, while higher or additional-rate taxpayers can claim further relief via Self Assessment.
Payroll Giving: Donations made directly from your wages or pension are deducted before tax, providing immediate relief.
Gifts of land, property, or shares: Tax relief is applied based on the market value of the assets at the time of donation.
Bequests in a will: Charitable donations in your will can reduce the Inheritance Tax due on your estate.

For limited companies, charitable donations result in reduced Corporation Tax, but the rules differ from individual contributions.

To claim tax relief, ensure you maintain accurate records of all donations, including receipts or confirmation from the charity.

Late filing penalties and appeal options

You’ll typically face penalties if you file your tax return late or miss a payment deadline, though you can appeal if you have a valid reason, often referred to as a “reasonable excuse.”

A standard £100 fine applies if your return is up to three months late or your payment is overdue. If the delay extends beyond three months, additional fines come into play. These include daily penalties and further charges based on the amount owed, often referred to as tax-geared penalties. Interest is also added to any unpaid amounts. HMRC offers an online tool to estimate your penalty.

If you’re worried about missing the deadline because your HMRC online account isn’t yet active, Charlie Walker advises that an accountant or tax adviser may be able to help. They can file your return through their agent access with HMRC.

We suggest filing early to avoid stress and reduce the risk of your return being scrutinized by HMRC. If you’re unable to meet the payment deadline, we recommends contacting HMRC as soon as possible. You might be able to arrange a payment plan or request an extension, but keep in mind that demand for HMRC’s online services and tax advisers increases as the deadline nears.

How to pay your tax

When filing your Self Assessment tax return online, HMRC will calculate the amount of tax you owe once your submission is complete.

Payments on account are calculated as two equal instalments, each representing half of the previous year’s tax bill. If there’s still an outstanding balance after these payments, a balancing payment is due by midnight on 31 January of the following year.

For payments made by debit card, ensure you allow at least two working days for the transaction to clear.

If you prefer to spread the cost throughout the year, HMRC offers a budget payment plan. This allows you to make regular payments (weekly or monthly), provided your previous tax payments are up to date and the payments are made in advance.

Payment methods

You can pay your tax bill through several methods, including online or telephone banking (Faster Payments), CHAPS, BACS, debit or corporate credit card online, direct debit (if previously set up with HMRC), or by cheque through the post. However, payments at the Post Office are no longer accepted.

For detailed instructions on each payment option, visit the “Pay your Self Assessment tax bill” section on HMRC’s website.

If your payment deadline falls on a weekend or bank holiday, ensure your payment reaches HMRC by the last working day before the deadline, unless you’re using Faster Payments or a debit/credit card.

Set aside money each month for your tax bill, especially if you’re in your first year of self-employment. A general guideline is to save 25% of your profits for tax or 33% if you’re a higher rate taxpayer.

Opening a dedicated savings account for this purpose can help you stay organized, and you’ll get to keep any interest earned on the funds.

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Frequently Asked Questions

Self Assessment is the system used by the UK government to collect information about income earned by sole traders, partnerships, or individuals with untaxed income to determine the tax they owe. You can submit your details either by completing a paper form or filing online through the HMRC website.

Company accounts consist of your company tax return as well as your complete annual statutory accounts. Statutory accounts refer to the yearly financial records prepared by your company at the end of every financial year. These records will be distributed to the Companies House and to HMRC to be used for your tax return.

If you earn income that isn’t taxed at source—for example, from freelancing, renting out property (even a single room or a holiday let), running a sole trader business, or pursuing a side hustle that exceeds £1,000 annually—you are required to report this to HMRC.

Additionally, this applies to earnings from taxable investments, such as dividends from shares or interest from savings accounts.

Earnings from these sources can impact your overall tax bracket, including any PAYE income, and may also affect benefits you claim. Therefore, it’s essential to accurately report all taxable income.

For example:

If you work part-time under PAYE, earning £10,000 annually, and generate an additional £5,000 from renting out a room, you must declare the rental income through Self Assessment, as your combined income exceeds the personal tax-free allowance of £12,570.

Similarly, if you earn £35,000 annually under PAYE and receive investment dividends and savings interest exceeding the tax-free thresholds—currently £2,000 for dividends—you must complete a Self Assessment tax return to account for this additional income.

Providing accurate records ensures you pay the correct tax and stay compliant.

The tax year ends on 5 April, and the new tax year begins on 6 April.

Key deadlines include:

31 January: The deadline for declaring earnings from the previous tax year and making the first payment on account if your income exceeds the threshold.

31 July: The due date for the second instalment of the payment on account, if applicable.

Additionally, this applies to earnings from taxable investments, such as dividends from shares or interest from savings accounts.

For example:

Providing accurate records ensures you pay the correct tax and stay compliant.

In 2026, the government will be implementing its Making Tax Digital scheme. This requires four statements a year, plus an end of year declaration if you earn more than £50,000 as a sole trader. In 2027, this will apply to anyone earning £30,000 or more.

In the Autumn Budget 2024, the new Labour Government said they were expanding the MTD scheme to apply to earners of £20,000 at some point in the future, though a date has not been set.

While there are no change to Self Assessment tax returns for anyone earning under those thresholds yet, it is not clear if MTD will be rolled out for everyone in the future.

Key deadlines include:

31 January: The deadline for declaring earnings from the previous tax year and making the first payment on account if your income exceeds the threshold.

31 July: The due date for the second instalment of the payment on account, if applicable.

Additionally, this applies to earnings from taxable investments, such as dividends from shares or interest from savings accounts.

For example:

Providing accurate records ensures you pay the correct tax and stay compliant.

How to file a Self Assessment tax return online:

A step-by-step guide

Are you preparing to file your tax return online before the Self Assessment deadline of 31 January? Does the process feel overwhelming, especially if you’re new to Self Assessment or unsure where to begin?

While some individuals file their tax returns as early as the first day of the new tax year, it’s okay if you’re not one of them. Filing online is the easiest and most efficient method, offering benefits like avoiding postal delays and giving you more time to meet the deadline.

Though the idea of filing online might seem intimidating—especially if you’re not tech-savvy—proper preparation can make it simpler than you think. Tackling it sooner rather than later can also prevent last-minute stress.

This guide will walk you through tips for completing your Self Assessment tax return online. It covers key topics such as important deadlines, penalties, allowable expenses.

Please note that this guide does not provide legal or professional advice. If you’re unsure about anything, please contact us for specialized assistance.

So, is filing a tax return online easy? The answer is yes—let’s get started.

This guide will cover the following:

WHO needs to file a tax return?

For employees and pensioners, taxes are typically deducted automatically at source from wages and pensions through the PAYE system.

However, individuals and businesses with additional income not taxed at source—such as rental income, dividends, or freelance earnings—must report it via a Self Assessment tax return if the income exceeds a certain threshold.

You must also file a return if you:

Were a partner in a business partnership.

Were a director of a limited company with untaxed income.

Earned more than £100,000 through PAYE.

Received untaxed income from sources like:

Rental properties.

Tips or commissions.

Savings, investments, or dividends.

Foreign income.

You may also file a return to claim income tax relief or prove self-employment status for benefits like Tax-Free Childcare or maternity allowance.

To check if you need to file, HMRC provides a decision tree tool.

Remember to register for Self Assessment by 5 October following the tax year you are declaring for. For the 2024–2025 tax year, the registration deadline is 5 October 2025.

Being informed and prepared can help you meet your obligations smoothly and avoid penalties.

Important dates and deadlines for Self Assessment

If you’ve registered for Self Assessment by the 5 October 2024 deadline for the 2023/24 tax year, there are several important dates to keep in mind:

Paper Tax Returns Deadline:Submit paper tax returns by midnight on 31 October 2024.

Online Tax Returns Deadline:File online tax returns by midnight on 31 January 2025.

Payments on Account

After filing your first tax return, you may need to make payments on account—advance payments towards your tax bill for the current tax year.

This applies if your last tax bill exceeded £1,000 or if less than 80% of your tax was already deducted at source (e.g., through PAYE). Payments are made in two instalments:

First Payment: Due by 31 January.

Second Payment: Due by 31 July.

Example Scenario

If Sarah owes £3,000 for her 2023/24 tax year, her total payment by 31 January 2025 would be £4,500. This includes:

£3,000 for the previous year’s tax.

£1,500 as the first instalment for her 2024/25 tax bill (50% of her expected total bill).

By 31 July 2025, she will need to pay the second instalment of £1,500.

If her income changes significantly in the following tax year, her payments on account will be adjusted accordingly in her next tax return.

By staying organized and aware of these deadlines, you can avoid penalties and manage your tax obligations more efficiently.

How to register and file a tax return online

For the 2022/23 tax year, 96% of tax returns were filed online, highlighting the convenience of this method. HMRC emphasizes that filing online is simple, secure, accessible 24/7, and allows you to sign up for email alerts and online messages for easier tax management.

Getting Started

If you’ve filed before but skipped the previous year, you’ll need to re-register for Self Assessment.

Before registering or completing the return, gather all the required information, including:

UTR and National Insurance number

Employer reference (if applicable)

Documents like your P60, P11D, P45, payslips, or P2 PAYE coding notice

Bank statements, profit/loss accounts (if self-employed), and other business records

Completing the Tax Return

The form is divided into several sections:

Personal Details: Start with your basic information.

Income Sources: Declare all sources of income, such as employment, self-employment, rental income, dividends, pensions, or overseas earnings. Answer “Yes” to relevant boxes to provide further details.

Additional Information: Declare items like student loans, charitable donations, pension contributions, or child benefit.

Ensure you report all income, even if you’re filing as a sole trader, as HMRC requires a complete overview. Use HMRC’s guide or supplementary pages for clarification if needed, and don’t send supporting documents unless requested by HMRC.

Filing Tips

Save your progress as you fill out the return—you can revisit and make changes before submission.

Double-check all figures before hitting submit.

Print a copy of your final return and the receipt for your records.

If there are major differences compared to previous returns, use the Further Information section to explain these changes.

Record-Keeping

You must retain all records used to complete your Self Assessment for at least five years after the 31 January filing deadline. This includes accounts and supporting documents. Failing to maintain adequate records may result in significant penalties if reviewed by HMRC.

By staying organized and carefully completing your return, you can navigate the process with confidence.

Claiming allowable expenses

If you’re self-employed, your business will have various operating costs. Many of these can be deducted as allowable expenses to calculate your taxable profit, provided they meet HMRC’s criteria. Common examples include:

Office-related costs: Such as stationery, phone bills, or internet.

Work-specific clothing: Uniforms or protective gear (note: regular clothing, including business suits, is not claimable).

Staff expenses: Salaries, wages, or subcontractor payments.

Financial charges: Insurance, bank charges, or business-related interest.

Professional fees: Some accountant or legal fees.

Business premises costs: Heating, lighting, and business rates, but not rent for a home office unless it’s exclusively used for work.

Advertising and marketing: Website development or promotional campaigns (excluding client entertainment).

Key Considerations for Tax Deductions

While HMRC’s online system calculates your tax liability, it doesn’t verify the accuracy of your figures or ensure you’ve claimed all eligible reliefs and allowances.

Common areas for tax relief, including:

Research and Development (R&D) expenditures.

Use of home as an office (within specified limits).

Capital allowances: Including full relief on eligible equipment under the Annual Investment Allowance (AIA).

Travel and accommodation when working away from home.

Paper Tax Returns Deadline:
Submit paper tax returns by midnight on 31 October 2024.

Online Tax Returns Deadline:
File online tax returns by midnight on 31 January 2025.