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

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

Although some deadlines may have passed, unresolved filings or payments linked to this period can still result in penalties, interest, or HMRC follow-up actionn, particularly where issues were not reviewed at the time with a tax consultant in London or equivalent professional support.

Key Tax and Payroll Deadlines for March and April 2025

• 1 March 2025 – Due date for Corporation Tax due for the year ended 31 May 2024.
• 2 March 2025 – Self-Assessment tax for 2023-24 paid after this date will incur a 5% surcharge unless liabilities are cleared by 1 April 2025, or an agreement has been reached with HMRC under their time to pay facility by the same date.
• 19 March 2025 – PAYE and NIC deductions due for month ended 5 March 2025 (If you pay your tax electronically the due date is 22 March 2025).
• 19 March 2025 – Filing deadline for the CIS300 monthly return for the month ended 5 March 2025.
• 19 March 2025 – CIS tax deducted for the month ended 5 March 2025 is payable by today.
• 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.

Why March and April Deadlines Still Matter

Tax obligations do not end once a deadline has passed. Where a return was not submitted or a payment was made late, HMRC may continue to treat the matter as outstanding until it is resolved.

This period also sits close to the end of the tax year, making it important to ensure that all outstanding matters are addressed before moving into the new tax year, something often highlighted during a later review by a tax specialist in London.

Common Obligations Around March and April

Deadlines during this period often relate to:

• Outstanding Self Assessment filing or payment issues
• VAT return submissions and payments
• PAYE and National Insurance reporting and payments
• Year-end compliance and reporting obligations

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 March or April 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 notice was issued, HMRC can still pursue the matter later, often after figures are revisited or clarified with a tax advisor in London.

Why It Is Worth Reviewing Now

Some taxpayers assume that once the tax year ends, earlier issues become less relevant. In practice, unresolved obligations can carry over and result in unexpected demands or compliance action.

Reviewing whether all March–April 2025 obligations were met can help reduce risk and avoid complications later in the year.

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 March or April 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 Hammersmith and nearby areas such as West Kensington and Olympia, CIGMA Accounting can review your position and confirm whether anything remains outstanding or needs to be addressed.