As the new year begins, January often brings more than just resolutions. It is also one of the busiest months for UK taxpayers because the Self-Assessment filing and payment is due.

With Self-Assessment deadlines, it’s important to stay on top of your tax responsibilities.

Missing deadlines can result in penalties and interest, which are not pleasant to deal with.  

Whether you’re a business director or an individual, managing your Self-Assessment for the first time, and complying with tax rules & regulation can be overwhelming.

At RedBrick, we are here to guide you every step of the way, offering expert advice and providing a home for your business or personal finances, so you can feel comfortable, secure, and relaxed.

In this comprehensive guide, we have tried to simplify the important tax deadlines for January 2025, common pitfalls to avoid, and practical steps to ensure you’re fully prepared.

Why January Is a Key Month for UK Taxpayers

As January starts, many UK taxpayers have one of the most important deadlines in the tax year. The Self-Assessment tax return for the 2023/2024 tax year must be submitted and paid by 31 January 2025.

This deadline is not just for individuals registered for self-employment, it applies to a range of taxpayers, including:

• Individuals with additional income not covered by PAYE, such as self-employed workers, landlords, investors, and those with foreign income.
• Businesses operating as sole traders or partnerships.
• Company directors or shareholders receiving taxable income from dividends or other sources (i.e. not through PAYE).
• Those earning over £150,000 (regardless of source)
• Those eligible for the High Income Child Benefit Charge

It’s not just about filing your return. Many taxpayers also need to:

1. Pay their balancing payment for the 2023/2024 tax year.

• Make the first payment on account in advance of the 2024/2025 tax year.

All of these can make January feel overwhelming. But with the right support and planning, you can avoid unnecessary stress and start the year on a correct and clear financial foundation.

Key Deadlines in January 2025

1. Self-Assessment Online Submission – 31 January 2025

Your online Self-Assessment tax return for the 2023/2024 tax year must be submitted by 31 January 2025.

What happens if you miss it?

An automatic £100 penalty will apply, even if you have no tax to pay or are owed a refund.

2. Balancing Payment for 2023/2024 – 31 January 2025

If you still owe tax for the 2023/2024 tax year, you can settle it.

What is this?

Your balancing payment is the remaining tax owed after considering any payments on account you made during the year. Clearing this payment ensures you avoid penalties.

If it is the first year you are completing your Self-Assessment, or you didn’t have a tax liability high enough in the previous year, you won’t have paid any payments on account.

3. First Payment on Account for 2024/2025 – 31 January 2025

This deadline also covers the first payment on account for the next tax year, 2024/2025.

What is a payment on account?

It’s an advance payment towards your next tax bill, based on half of your tax liability for the previous year. If your circumstances have changed and you expect to earn less, you can also apply to reduce this amount.

4. Corporation Tax Payments (Variable Deadlines)

For companies with taxable profits, Corporation Tax payments might also be due in January, but the exact deadline depends on your accounting period.

Corporation Tax payments for small companies are due 9 months and 1 day after the end of your accounting period.

So for small companies with accounting periods ending between 31^st March 2024 and 30^th April 2024, Corporation Tax will also be due in January 2025.

What should you do?

Check your Corporation Tax due date and ensure it’s marked in your calendar to avoid late payment penalties.

The Risks of Missing Tax Deadlines

Missing tax deadlines can lead to serious financial, reputational, and legal consequences. Here are the key risks and why staying on top of your tax obligations matters.

• Financial Penalties:

Failing to file your Self-Assessment tax return by the deadline can trigger an automatic £100 fine, even if you do not owe any tax. The longer the delay, the higher the penalties:

• After 3 months: Daily penalties of £10 (up to £900).
  • After 6 months: Additional penalties of 5% of the tax due (or £300, whichever is greater).
  • After 12 months: Further 5% penalties, plus potential additional charges. 

• Interest Charges:

If you don’t pay your tax on time, daily interest starts building up from the day after the deadline. Over time, these charges can add significantly to your overall bill, compounding your financial burden.

• HMRC Investigations:

Repeatedly missing deadlines or failing to pay can raise red flags with HMRC, increasing your chances of facing an audit or investigation. These can be:

• Time-consuming: Going through numerous records and responding to HMRC queries takes time.
  • Stressful: Investigations are rarely straightforward and can lead to further penalties if issues are uncovered.
  • Costly: HMRC can go back up to 20 years! This depends on whether it considers errors innocent, careless, or deliberate.

• Reputational Damage:

For businesses, tax non-compliance isn’t just about fines and interest—it can also harm your reputation.

Late or missed payments might:

• Undermine trust with suppliers, investors, and customers.
• Damage your reputation, particularly if word of non-compliance spreads.

How to Prepare for January 2025 Tax Deadlines

With the right preparation, you can ensure a smooth and seamless process. Here are five practical steps to help you stay on track:

1. Gather Your Financial Records

Start by collecting everything you’ll need for your tax return: income statements, expense receipts, bank statements, and any investment records. Keeping your records organised not only ensures accuracy but also helps you avoid costly mistakes. Time spent upfront saves you time and money later on.

2. Digital Technology Implementation

Using cloud-based digital tools, such as accounting software like Xero or FreeAgent for businesses, or even just Excel for individuals, can make life so much easier. These tools help you manage your records, automate calculations, and meet HMRC’s Making Tax Digital (MTD) requirements with minimal effort.

There are a lot of changes happening in this space, in anticipation of Making Tax Digital Income Tax Self-Assessment (MTD ITSA) in 2026.

3. Check Your Allowances and Reliefs

Claim all the tax reliefs and allowances you’re entitled to, such as personal allowances, business expenses, or capital gains tax exemptions. These can change regularly, with new one’s being added, or old one’s withdrawn, so it’s always worth re-checking each year.

4. Review Payments on Account

Has your income changed significantly since last year? If so, you might be paying more than you need to on your payments on account. Consider applying to reduce them. It is a simple way to free up cash flow.

5. Partner with Professionals

Working with a trusted and experienced accounting firm like RedBrick can reduce the pressure. We’ll ensure your return is accurate, compliant, and submitted on time, giving you peace of mind.

Common Mistakes to Avoid

Here are some of the most common errors people make and how to avoid them.

1. Procrastination

Leaving your Self-Assessment tax return until the last minute can cause stress and mistakes. Give yourself plenty of time to gather your records, check your figures, and resolve any issues before the deadline. Setting automated calendar reminders can help you stay on track.

2. Not Leaving Enough Time For Payments To Reach HMRC

Paying too close to the deadline can mean that your payment is received by HMRC 1 or 2 days late, and you receive a penalty. Set up payments with plenty of time for them to be received, so this does not happen to you.

3. Failing to Budget for Payments

Unexpected tax bills can complicate your finances. Plan by setting aside funds throughout the year to cover payments. This ensures it does not come as a shock or surprise. Similarly, if you invest your surplus cash, be sure to factor in market volatility and unforeseen circumstances outside your control.

4. Overlooking Income Sources

Ensure all taxable income is included in your tax return, including rental income, dividends, and overseas earnings. Omissions can result in penalties. HMRC assesses your ‘Total Worldwide Income from all sources’.

5. Misunderstanding Tax Reliefs

Failing to claim eligible deductions or reliefs can result in overpaying tax. Many taxpayers miss out simply because they’re unaware of what’s available or assume it doesn’t apply to them. Even small claims, like working-from-home expenses, can add up over time and make a real difference.

How RedBrick Can Help

At RedBrick, we understand the complexities of tax compliance and the stress it can cause. That’s why we offer tailored accounting and advisory services designed to reduce your pressure.

Here’s how we can help:

• Self-Assessment Support: From preparing and submitting your tax return to addressing HMRC queries, we can handle it all.
• Remote FinOps Services: Our team can manage everything from bookkeeping and payroll to financial modelling, helping you streamline your processes, plan for the future, and stay on top of your finances.
• Digital Transformation: We can help you adopt and integrate advanced accounting tools, ensuring compliance with MTD requirements, and reducing the time you need to spend.
• Proactive Tax Planning: We can provide strategic advice to minimise your tax liability and maximise financial efficiency.
• Ongoing Support: With RedBrick by your side, you’ll have year-round access to expert guidance, helping you navigate challenges and seize opportunities. We prioritise Human Values & Connections, ensuring you are always heard and understood, and ‘Feel At Home’ with your finances.  

Final Thoughts

Tax compliance doesn’t have to be stressful. By getting a clear understanding of your obligations, planning ahead, and seeking expert help, you can easily navigate through the January 2025 tax deadlines with confidence.

At RedBrick, we’re here to make the whole process smoother, helping you meet your tax responsibilities while optimising your financial health.

Never miss a tax deadline again. Get in touch with RedBrick today to learn how we can support you achieve your financial goals and build a better home for your finances.

NB: This article was correct at the time of writing, but the rules, rates, and allowances change each tax year, so if you are reading it after the fact, you should update accordingly. Note that this article does not constitute financial advice, which will be dependent upon your individual circumstances. You are fully liable for any decisions you choose to make.