United Kingdom · employment

How Long Do I Have to Claim Unfair Dismissal UK

In the UK, you have a very narrow window to claim unfair dismissal. The baseline limit is strictly three months less one day from your dismissal date. Acting fast and understanding how ACAS conciliation pauses this clock is essential to preventing HR from running down your time.

The Strict Deadline Under UK Law

If you have been unfairly dismissed in the United Kingdom, the law is unforgivingly strict about time. Under Section 111 of the Employment Rights Act 1996, you generally have just three months less one day from your 'Effective Date of Termination' (EDT) to bring a claim to an Employment Tribunal. For example, if your last day of employment was 4th November, your absolute deadline to act is 3rd February of the following year.

Corporate HR departments are well aware of this tight window. They may try to drag out internal grievance processes or appeal hearings in an attempt to run down your clock and escape liability. Do not fall into this trap: the law is clear that pursuing an internal appeal does not pause or extend the statutory three-month tribunal deadline.

The ACAS 'Stop the Clock' Rule & Recent EAT Precedent

Before you can submit an Employment Tribunal claim, UK law requires you to notify the Advisory, Conciliation and Arbitration Service (ACAS) for Early Conciliation. Under Section 207B of the Employment Rights Act 1996, starting this process temporarily pauses—or 'stops the clock' on—your three-month deadline while conciliation takes place.

However, timing this pause is critical. In the landmark case of Raison v DF Capital Bank Ltd [2025] EAT 86, the Employment Appeal Tribunal clarified that if you initiate ACAS conciliation before your actual dismissal date (for instance, during your notice period), those pre-dismissal days do not pause or extend your three-month limit because the limitation clock hasn't legally started running yet. Only the conciliation days that fall after your dismissal date will pause the clock. Miscalculating this by even a single day can result in your claim being struck out entirely.

How to Protect Your Claim Today

You do not have to let HR's delay tactics or complex tribunal math defeat your claim. Because the rules on calculating extension days are highly technical, you must take control of your situation immediately. Compile your employment contract, dismissal letter, and any internal emails or messages regarding your termination.

If you need help staying on top of deadlines or want professional guidance, you can use Caunsel to research this issue further, securely save your evidence and documents in a dedicated digital case, or consult with an independent lawyer to verify your exact tribunal deadlines.

Steps

• Identify your exact Effective Date of Termination (EDT)—this is usually your last day of notice, or the day you were fired if dismissed without notice.
• Calculate your baseline deadline, which is exactly three months less one day from your EDT.
• Contact ACAS to initiate Early Conciliation before your baseline deadline expires to legally pause the countdown.
• Retrieve your ACAS Certificate once conciliation ends and calculate your final, extended tribunal filing deadline.

Common mistakes

• Assuming that an ongoing internal appeal or grievance process pauses the strict three-month tribunal time limit.
• Initiating ACAS Early Conciliation before your dismissal date and assuming the entire conciliation period extends your post-dismissal deadline.
• Waiting for the ACAS certificate to arrive before gathering your evidence and preparing your ET1 tribunal claim form.

Questions people ask

What is the Effective Date of Termination (EDT)?

Your EDT is the date your employment contract officially ends. It is usually your last day of notice, or if you were summarily dismissed on the spot without notice, it is the day you were fired.

Can I get an extension if I miss the three-month deadline?

Under Section 111(2)(b) of the Employment Rights Act 1996, tribunals can extend the deadline only if it was 'not reasonably practicable' to file on time. This is an incredibly high bar; simply not knowing the deadline or waiting for an internal appeal result is almost never accepted as an excuse.

What happens if I contact ACAS with less than one month left on my clock?

If you contact ACAS within your final month of limitation, the law provides a 'grace period' extension. You will have at least one full calendar month from the date you receive your ACAS Early Conciliation certificate to file your claim.

General information only, last updated 2026-09-11. Caunsel is not a law firm and does not practise law. AI answers and this guide are not legal advice. Verify filings, deadlines, and statutes with a licensed lawyer in United Kingdom.