You are free to resign at any time - the employer cannot refuse to accept your resignation. However, if you were to resign you would be required to give them the notice period in your contract, which you have confirmed is 2 months. You would be expected to continue working as normal during that period, unless they agree to let you go earlier. What could happen is that you give in your notice and start working the 2 month notice period, only for the employer to still proceed with the performance plan which is shorter than your notice period.
You could try and negotiate with them to just let you go and remind them that doing so would save them time and resources by not having to take you through the full performance procedure.
If they refuse to do so, you either have to continue there for the notice period, or take the risk and leave with immediate effect. However if the employee fails to honour their notice period they will be acting in breach of contract. Whilst no one can physically force them to work through their notice period, it would instead allow the employer to sue them for compensation for losses/damages resulting from their breach.
In reality such claims are very rarely made. This is mainly due to the costs and time involved, also the relatively small damages that can be recovered. The employer has to show that actual losses have been incurred and often that is not easy to do. The most common damages they would claim for are if they have to engage temporary cover for the employee’s duties and the extra wages they have to pay them or recruitment fees for recruiting a replacement at short notice.
So whilst there is no way of predicting whether the employer will take this any further, chances are that they will not. A more likely outcome is that the employer refuses to provide a reference in the future or if they do, it could mention that the employee had breached their contract.
It is therefore best to try and negotiate a mutually acceptable notice period that would suit both parties. However, if that is not possible and there is a pressing need to leave early, that is still a possibility, subject to the risks identified above.
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