In most Unfair Dismissal claims, the Employment Tribunal must receive your claim within 3 months less one day, from the date your employment ended. This is a rule robustly administered by the Tribunal so it is vital you get your claim in on time.
For discrimination claims or complaints relating to non payment of salary or holiday pay, the 3 month period begins from the date of the act complained of (which may be continuing, in which case the time for commencing proceedings will also continue to run).
The above time limit for issuing a Tribunal claim can, however, be extended. This can happen, because before you issue a claim, you will need to notify ACAS within the above 3 month period of your intention to issue proceedings, thus invoking its “early conciliation service”.
After you contact ACAS, the time limit for making a claim to the tribunal is automatically “paused” for up to one calendar month, plus a further 14 days if more time is needed for conciliation. This is to allow a sufficient period for ACAS to try to resolve the dispute, assuming all parties wish to do so.