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.