Employment Tribunal Time Limits: 3 Months Less 1 Day, Explained

Employment tribunal claims have some of the strictest deadlines in the civil justice system. For most claims the employment tribunal time limit is 3 months less 1 day from the event you are complaining about - and in practice, missing it almost always bars the claim, no matter how strong the underlying facts. This guide explains the rule claim by claim, exactly when the clock starts, how ACAS pauses it, and the narrow discretions tribunals have to accept a late claim.

If you want your own dates worked out rather than the rules in the abstract, our free tribunal deadline calculator does the arithmetic for you: enter your trigger date and it shows your ACAS notification deadline and your post-certificate filing window.

The general rule: 3 months less 1 day

For most employment tribunal claims, two things must happen in time:

1. You must notify ACAS to start Early Conciliation within 3 months less 1 day of the trigger event. The duty to notify ACAS before bringing a claim is set out in section 18A of the Employment Tribunals Act 1996.
2. After ACAS issues your certificate, you must file your ET1 claim form within the post-certificate window explained below.

"3 months less 1 day" is exact. If your last day of work was 15 January, your deadline to contact ACAS is 14 April - not 15 April. For unfair dismissal the time limit comes from section 111 of the Employment Rights Act 1996; for discrimination, from section 123 of the Equality Act 2010.

A small number of claims have different limits. The table below sets out the main ones.

When does the clock start?

The time limit is only half the question. The other half is the trigger date - the day the clock starts running. It varies by claim type (see the GOV.UK guidance on time limits):

Three trigger dates cause most of the confusion in practice.

Unfair dismissal: the effective date of termination. This is usually your last day of employment. If you worked your notice, it is the day the notice period expired. If you were dismissed without notice and paid in lieu, it is normally the day you were actually dismissed - not the day a paid-in-lieu period would have run to. If the date is ambiguous, take the earliest plausible date and calculate from that.

Discrimination: the act, or the last act in a continuing series. Section 123 of the Equality Act 2010 treats "conduct extending over a period" as done at the end of that period. So if you faced a connected course of discriminatory treatment, the clock runs from the last act in the series. But whether conduct really was "continuing" is decided by the tribunal after the event, and isolated incidents months apart may not qualify. The safer approach is to calculate from the first incident you want to complain about, not the last.

Unpaid wages: the last deduction in a series. For unlawful deductions from wages, the clock runs from the date of the last deduction in a series of linked deductions - which matters where the underpayment happened month after month.

How does ACAS pause the clock?

You cannot file an ET1 without an ACAS Early Conciliation certificate. The good news is that notifying ACAS pauses the deadline clock. Two dates matter:

• Day A - the day you notify ACAS to start Early Conciliation
• Day B - the day ACAS issues your certificate

The time between Day A and Day B does not count towards your deadline. Conciliation can run for up to 12 weeks (for notifications made on or after 1 December 2025), extendable by a further 14 days if both sides agree. After Day B you get whichever is longer:

• the time you had left on the original deadline when you notified ACAS, or
• 1 month from the certificate date.

A worked example

Say you were dismissed on 10 March.

1. The original deadline. 3 months less 1 day from 10 March is 9 June. You must notify ACAS by that date.
2. You notify ACAS on 20 April (Day A). At that point you have 50 days left on the clock - 20 April to 9 June.
3. ACAS issues your certificate on 15 May (Day B). The 25 days of conciliation did not count against you.
4. The clock restarts with your 50 days intact. 50 days from 15 May takes you to 4 July.
5. The 1-month-minimum check. One month from the certificate would be 15 June. You get whichever is longer - so 4 July is your ET1 filing deadline.

The one-month minimum exists to protect people who notify ACAS very close to the deadline: even if you had only 2 days left on the clock at Day A, you still get a full month from the certificate to file. The statutory counting rules have technical edge cases, so treat any manual calculation as provisional - the tribunal deadline calculator applies the rules for you, and the tribunal's own decision on the dates is final.

For what actually happens during conciliation - what to tell ACAS, how settlement discussions work, what the certificate looks like - see the ACAS Early Conciliation guide.

What if you miss the deadline?

Treat the deadline as hard. In practice, missing it almost always bars the claim. Tribunals do have a discretion to accept late claims, but the tests are strict and the starting point is always that the limit applies.

"Not reasonably practicable" - unfair dismissal and most other claims. Under section 111 of the Employment Rights Act 1996, the tribunal can accept a late unfair dismissal claim only if it was not reasonably practicable to bring it in time, and it was then brought within a reasonable further period. This is a strict test. "I did not know about the time limit", "I was waiting for my internal appeal", or "I was hoping to settle" almost never succeed. Serious incapacitating illness, or being actively misled about a fact essential to the claim, occasionally can.

"Just and equitable" - discrimination claims. Under section 123 of the Equality Act 2010, the tribunal can extend time where it considers it just and equitable to do so. This is broader than the unfair dismissal test and gives the tribunal a genuine discretion - but extensions remain the exception, not the rule, and a tribunal is entitled to refuse one even where the delay was short and the claim looked strong.

Either way, the practical rule is the same: do not plan around the discretion. If the deadline has not yet passed, contacting ACAS today is worth more than any extension argument you could make later.

Is the time limit changing to 6 months?

Probably - but not yet. The Employment Rights Act 2025 extends the standard employment tribunal time limit from 3 months to 6 months for most claims. The change is currently targeted for October 2026, but it is not yet in force and depends on commencement regulations. Two cautions:

• Until commencement, the 3 months less 1 day rule applies. Check the current position before relying on the longer limit.
• Breach of contract claims in the tribunal are expected to stay at 3 months even after the change.

See the Employment Rights Act 2025 guide for the wider package of reforms and their expected timing.

Protecting your deadline

• Contact ACAS as soon as you think you might have a claim. It is free, it is confidential, and notifying pauses the clock - you do not need to have decided anything first.
• Do not wait for a grievance or internal appeal to finish. Internal processes do not stop the tribunal clock.
• Keep dated records of the key events: your last working day, the dismissal letter, each discriminatory act, the dates payments were due.
• Calculate carefully, then check. Work out your trigger date, apply 3 months less 1 day, and run the dates through the deadline calculator rather than trusting mental arithmetic.

The single most common way people lose the right to bring a tribunal claim is the calendar, not the merits. If the clock is ticking, your priority is ACAS - everything else (drafting the ET1, gathering evidence, working out what your claim is worth) can come after.