If you both have signed the same document then there exists a contract between you and the other party. For claiming damages from you for not joining the job, there should be a clause in the contract stating the same. Also, if it has been specifically mentioned in the contract about revoking the contract before a specific time only then you would be liable to pay. Section 5 of The Indian Contract Act, 1872 talks about revocation of proposal and acceptance. You also need to know all the terms and conditions which were mentioned in the contract like whether the contract stated that if you don’t join, you have to pay for not joining. Please examine the terms of the contract to identify if the contract requires you to pay such an amount.