Tax Diary: March to April 2023

This tax diary covers key tax deadlines that fell between March and April 2023 and is relevant for taxpayers who want to check whether any obligations from that period were missed.

Although these dates have passed, unresolved filing or payment issues linked to them can still lead to penalties, interest, or HMRC follow-up action.

Key UK Tax Deadlines for March and April 2023

• 1 March 2023 – Due date for Corporation Tax due for the year ended 31 May 2022.
• 2 March 2023 – Self-Assessment tax for 2021-22 paid after this date will incur a 5% surcharge unless liabilities are cleared by 1 April 2023, or an agreement has been reached with HMRC under their time to pay facility by the same date.
• 19 March 2023 – PAYE and NIC deductions due for month ended 5 March 2023 (If you pay your tax electronically the due date is 22 March 2023).
• 19 March 2023 – Filing deadline for the CIS300 monthly return for the month ended 5 March 2023. 
• 19 March 2023 – CIS tax deducted for the month ended 5 March 2023 is payable by today.
• 1 April 2023 – Due date for Corporation Tax due for the year ended 30 June 2022.
• 19 April 2023 – PAYE and NIC deductions due for month ended 5 April 2023. (If you pay your tax electronically the due date is 22 April 2023).
• 19 April 2023 – Filing deadline for the CIS300 monthly return for the month ended 5 April 2023. 
• 19 April 2023 – CIS tax deducted for the month ended 5 April 2023 is payable by today.
• 30 April 2023 – 2021-22 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 Past Tax Diary Deadlines Are Still Relevant

Tax deadlines do not become irrelevant simply because time has passed. Where a return was not submitted or a payment was made late, the matter can remain open until it is resolved.

This means March and April 2023 deadlines may still affect you today if HMRC considers an obligation outstanding, even if you now rely on professional accounting services in London to manage your current compliance.

Common Obligations Around March and April

Deadlines during this period often relate to:

• Self Assessment filing and payment 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, an employer, or VAT-registered.

What Happens If a Deadline Was Missed?

If a tax deadline from March or April 2023 was missed, HMRC may have issued penalties or charged interest.

In some cases, penalties increase over time until the return is filed or the payment is made. Even where no immediate penalty was raised, HMRC may still pursue the issue later, especially where returns or payments were not supported by proper accounting services in London at the time.

Why It Is Worth Reviewing Now

Some taxpayers assume older deadlines no longer matter. In practice, unresolved issues often resurface through HMRC reminders, statements of account, or compliance checks.

Reviewing whether all obligations from March to April 2023 were met can help avoid unexpected demands or enforcement action.

HMRC Guidance on Late Tax Deadlines

HMRC provides guidance on late filing, late payment, and the penalties and interest that may apply on
GOV.UK.

Did You Miss Any March or April 2023 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 Hampton Wick and Long Ditton, CIGMA Accounting can review your position and confirm whether anything remains outstanding or needs to be corrected.