Two Important Self Assessment Deadlines in 2025

This guide is for UK Self Assessment taxpayers who need to be aware of two key deadlines falling in 2025 and want to understand what each date relates to. , including those who now use making tax digital services in London as part of their compliance.

While Self Assessment is often associated with a single deadline, there are two important dates in 2025 that can affect when your return must be filed and when tax is due, regardless of whether you file under traditional Self Assessment or through making tax digital services in London.

The First 2025 Self Assessment Deadline

The first key date in 2025 is 31 January. This is the deadline for filing your online Self Assessment tax return for the previous tax year and for paying any tax owed for that year.

It is also the date when the first payment on account may be due for the current tax year, depending on your circumstances.

The Second 2025 Self Assessment Deadline

The second important date in 2025 is 31 July. This deadline applies to taxpayers who are required to make a second payment on account towards their current tax year’s liability.

Not everyone will have a July payment due, but for those who do, missing this date can lead to additional charges.

Why These Deadlines Matter

Each deadline serves a different purpose. The January deadline focuses on filing and settling the previous year’s tax, while the July deadline relates to paying tax in advance.

Understanding which of these deadlines applies to you helps avoid unexpected bills and ensures you stay compliant with HMRC requirements.

Penalties and Interest for Missing a Deadline

If you miss the 31 January filing deadline, HMRC will usually issue an automatic £100 penalty, even if no tax is owed or the tax is paid on time.

Late payment interest may also apply to any unpaid tax. If a payment on account due on 31 July is missed, interest will normally be charged from the day after the deadline until the amount is paid.

HMRC Guidance on Self Assessment Deadlines

HMRC’s official guidance on Self Assessment filing and payment deadlines is available on
GOV.UK.

Which 2025 Deadlines Apply to You?

Not every Self Assessment taxpayer will be impacted in the same way by the two deadlines. For individuals based in Wimbledon and nearby areas such as Colliers Wood and New Malden, whether you need to file a return, make a payment on account, or deal with both will depend on your personal tax position. At CIGMA Accounting, we can help you clarify which obligations apply to you and what action is actually required.

Need Help Meeting the 2025 Self Assessment Deadlines?

Failing to notify HMRC by the 5 October deadline or miss the paper return date can result in penalties and interest. Specialist guidance can help you confirm your filing obligations, plan your deadlines and manage any late filing risk.

Speak to a Specialist About 2025 Deadline Planning

Trusted guidance from London-based accountants, focused on accuracy, clarity, and compliance. 


author avatar
Aitch
I'm Aitch, the Founder and CEO of CIGMA Accounting Ltd. As a Chartered Management Accountant and as a CIMA member, I've spent more than 16 years helping businesses, entrepreneurs, landlords, and individuals with tax planning, accounting, and HMRC compliance. As a chartered accountant in London, I'm passionate about making complex tax matters easier to understand and helping clients make confident financial decisions. Over the years, I've advised start-ups, SMEs, established companies, and high-net-worth individuals across a wide range of tax and accounting matters. My expertise includes Corporation Tax, Self-Assessment, Capital Gains Tax, Inheritance Tax planning, R&D tax relief, capital allowances, international tax, and resolving complex HMRC compliance issues. Whether clients need a business accountant, tax accountant, or strategic tax advisor, my focus is always on delivering practical advice that creates long-term value. One of my specialist areas is Making Tax Digital (MTD). I've worked extensively with businesses preparing HMRC's digital reporting requirements, helping them move to cloud accounting, improve financial processes, and adopt technology that makes compliance more efficient. I regularly speak at Making Tax Digital roadshows, industry events, and educational sessions in collaboration with Zoho Books, sharing practical insights into digital accounting, tax legislation, and the future of the profession. Many business owners looking for the best accounting firm in London are not simply searching for an accountant they're looking for trusted advice, responsive support, and long-term value. That's the approach I've taken in building CIGMA Accounting. My team and I work closely with businesses across London and the UK, providing accounting services, tax advisory, bookkeeping, payroll, VAT, company accounts, and strategic tax planning tailored to each client's goals. Through this website, I share practical guidance on UK taxation, Making Tax Digital, HMRC updates, Corporation Tax, Self-Assessment, and business finance. My aim is to provide reliable, straightforward information that helps business owners understand changing regulations, reduce compliance risks, and make informed financial decisions with confidence.
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