Is a resignation letter binding once submitted, or can I withdraw it?

You can certainly request to withdraw your resignation, but whether your employer is legally obligated to accept that withdrawal generally depends on whether it has already been formally accepted by the employer — once a resignation is accepted, it typically becomes a completed, mutual act that the employer isn't automatically required to reverse, even if you have a genuine change of heart.

If your resignation hasn't yet been formally accepted, or if your notice period hasn't yet run its course, you're generally on stronger ground to request withdrawal, and many employers are willing to accommodate this, especially where there's no independent reason (like a decision to eliminate your role) driving the situation.

Act quickly — send your withdrawal request in writing as soon as possible, explaining your position clearly, since delay can weaken your case if the employer has, in the meantime, already started proceeding on the basis that you're leaving (such as beginning to hire your replacement). If your employer refuses to accept a timely withdrawal, it would be worth getting a labour lawyer's view on your specific situation.