Tax Diary: April to May 2025 Deadlines That May Still Matter

This tax diary highlights key UK tax deadlines that fall between April and May 2025. It is relevant for taxpayers reviewing whether all obligations from this period were dealt with correctly.

Although these dates may have passed, unresolved filings or payments from this period can still result in penalties, interest, or HMRC follow-up action.

Key Tax and Payroll Deadlines for April and May 2025

• 1 April 2025 – Due date for corporation tax due for the year ended 30 June 2024.
• 19 April 2025 – PAYE and NIC deductions due for month ended 5 April 2025. (If you pay your tax electronically the due date is 22 April 2025).
• 19 April 2025 – Filing deadline for the CIS300 monthly return for the month ended 5 April 2025.
• 19 April 2025 – CIS tax deducted for the month ended 5 April 2025 is payable by today.
• 30 April 2025 – 2023-24 tax returns filed after this date will be subject to an additional £10 per day late filing penalty for a maximum of 90 days.
• 1 May 2025 – Due date for corporation tax due for the year ended 30 July 2024.
• 19 May 2025 – PAYE and NIC deductions due for month ended 5 May 2025. (If you pay your tax electronically the due date is 22 May 2025).
• 19 May 2025 – Filing deadline for the CIS300 monthly return for the month ended 5 May 2025.
• 19 May 2025 – CIS tax deducted for the month ended 5 May 2025 is payable by today.
• 31 May 2025 – Ensure all employees have been given their P60s for the 2024/25 tax year.

Why April and May Deadlines Still Matter

Tax obligations do not end once a deadline has passed. Where a return was not filed or a payment was made late, the obligation remains open until it is resolved.

April is a critical time, especially with Self Assessment payments due and other year-end filing responsibilities. Delays can have lasting consequences, sometimes only becoming apparent later through HMRC correspondence or a review by a tax specialist in London.

Common Obligations Around April and May

Deadlines during this period often relate to:

• Self Assessment payment deadlines
• Self Assessment filing obligations
• VAT return submissions and payments
• PAYE and National Insurance reporting and payments

Which obligations applied will depend on your circumstances, such as whether you were self-employed, a landlord, an employer, or VAT-registered.

What Happens If a Deadline Was Missed?

If a tax deadline in April or May 2025 was missed, HMRC may have applied penalties or charged interest from the original due date.

In some cases, penalties increase the longer an issue remains unresolved. Even where no immediate penalty notice was issued, HMRC can still raise the matter later, particularly where records or calculations are revisited with a tax advisor in London or during an HMRC check.

Why It Is Worth Reviewing Now

Some taxpayers assume that missing early-year deadlines has little impact. In practice, unresolved obligations can carry over and result in unexpected demands or enforcement action later in the tax year.

Reviewing whether all April–May 2025 obligations were met can help avoid additional costs or compliance risks.

HMRC Guidance on Late Tax Deadlines

HMRC explains how penalties and interest apply to late filings and payments on
GOV.UK.

Did You Miss Any April or May 2025 Deadlines?

Whether any action is required now will depend on which obligations applied to you at the time and whether they were dealt with correctly. For individuals and businesses in Kingston upon Thames and nearby areas such as Surbiton and Tolworth, CIGMA Accounting can review your position and confirm whether anything remains outstanding or needs to be addressed.