In this blog, we’ll guide you through the key deadlines for submitting your return and explain the penalties you could face if deadlines are missed.

Who Needs to Complete a Self Assessment Tax Return?

First, it’s worth identifying who exactly needs to submit a Self Assessment tax return. You’ll likely need to file if you:

• Are self-employed or a sole trader earning over £1,000 per year


• Earn over £2,500 in untaxed income (like from renting out property)


• Have savings or investment income over £10,000 before tax


• Are a director of a company (unless it’s a non-profit)


• Earn over £100,000 per year


• Claim child benefit, and you or your partner have an income over £50,000


• Have foreign income you need to declare


• Are a partner in a business partnership

These are just a few examples. In some cases, HMRC may send you a notice telling you that you need to complete a tax return. Even if you don’t think you need to submit a return, it’s a good idea to double-check your status with HMRC to avoid any potential penalties later.

Key Deadlines to Remember

To stay on top of your tax affairs, you must meet several important deadlines throughout the tax year. Missing these deadlines can result in penalties and added stress, so it’s vital to mark them in your calendar.

1. Register for Self Assessment

If you’re filing a Self Assessment tax return for the first time, you’ll need to register with HMRC. The deadline for registering is 5th October following the end of the tax year in which you need to file a return. For example, if you need to file for the 2023/24 tax year, you should register by 5th October 2024.

2. Paper Tax Return Submission

If you prefer to file a paper tax return instead of doing it online, the deadline for submitting your paper return is 31st October. This is well ahead of the online filing deadline, so make sure to give yourself plenty of time if this is your preferred method.

3. Online Tax Return Submission

The more common way to file your return is online. For online submissions, the deadline is 31st January following the end of the tax year. For the 2023/24 tax year, for instance, you’ll need to file by 31st January 2025.

4. Paying Your Tax Bill

The deadline to pay any tax you owe is also 31st January. You can pay your tax bill via bank transfer, direct debit, cheque, or using a debit or credit card. Be sure to leave yourself enough time to arrange your payment, as late payments will incur interest and penalties.

5. Payments on Account

If you are self-employed or earn additional untaxed income, you may be required to make payments on account. These are advance payments towards your next tax bill, due in two instalments:

• First payment on account: 31st January


• Second payment on account: 31st July

Payments on account are usually based on your previous year’s tax bill. If your income for the current year is significantly lower, you can apply to reduce these payments.

Penalties for Missing Deadlines

Failing to file your tax return or pay your tax bill on time can result in hefty penalties. Here’s a breakdown of the fines you could face:

1. Late Filing Penalties

If you miss the filing deadline, even by one day, you’ll face an immediate fine. Here’s what you could expect:

• £100 fine for filing your return even one day late.


• If your return is more than 3 months late, you’ll face a penalty of £10 per day for up to 90 days (a maximum of £900).


• If your return is still outstanding after 6 months, you’ll face either a 5% penalty of the tax due or a fixed £300 fine, whichever is greater.


• After 12 months, another 5% or £300 penalty will be added.

In some cases, if HMRC believes you’re deliberately withholding information or income, the penalties could increase even further.

2. Late Payment Penalties

Late payment of your tax bill also incurs penalties, which escalate the longer you delay payment:

• 5% of the tax due if it’s 30 days late


• An additional 5% after 6 months


• Another 5% after 12 months

It’s important to note that HMRC will also charge interest on any unpaid tax from the date it’s due, which is added on top of the penalties.

Avoiding Penalties and Staying Organised

Keeping on top of deadlines is crucial to avoiding fines and penalties. Here are a few tips to help you stay organised:

1. Set reminders
   It can be easy to forget deadlines, especially if you’re busy running a business or juggling multiple jobs. Set calendar reminders a few months in advance of the key dates to give yourself enough time to gather information and submit your return.


2. Get professional help
   If you’re not comfortable filing your own tax return or want to make sure you’re taking full advantage of allowances and deductions, consider hiring an accountant or tax advisor. They can help ensure your return is accurate and filed on time, reducing the risk of penalties.


3. Keep detailed records
   Good record-keeping is essential for completing your tax return accurately. Keep a file of your invoices, receipts, and any other documents that relate to your income and expenses throughout the year. This will save you a lot of stress when it comes to filing your return.


4. File early
   Many people leave their tax return until the last minute, but filing early can give you peace of mind and allow you to spread out any tax payments you need to make. The sooner you submit your return, the sooner you’ll know how much you owe.

Final Thoughts

The Self Assessment tax return process can seem daunting, but by staying organised and keeping on top of deadlines, you can avoid penalties and ensure your tax affairs are in order. If you’re unsure about any part of the process, seek advice from a tax professional or visit the HMRC website for further guidance. Remember, missing deadlines can be costly, so take the time to plan and submit your return on time.