We must distinguish between the recognition of the transaction invalid or void. The agreement shall be invalid only by a court decision, and a paltry deal may not be challenged. Void contract is recognised if it is concluded in violation of the law, in violation of the norms of morality, if one of the partners is incapacitated or if the contract is imaginary, that is, the parties initially did not intend to perform the action stated in the contract. Also lawyers allocate a sham transaction, which is aimed to cover a some other, often illegal contract.
Gather all the necessary evidence that the contract is void. Will need the original of the contract and the papers that will confirm that one of the persons who entered into the transaction, was incompetent at the time of its conclusion. For example, a prenuptial agreement do not have the right to conclude a person under 18 years of age. If you are sure that the agreement was imaginary or feigned, it is also necessary to prove.
Make a claim about recognition void the agreement and submit it to the civil court. The statement shall describe in detail all circumstances that allows you to conclude the nullity of the transaction.
Consult with a professional lawyer. A layman in this area will be difficult to understand the intricacies of legal terms: what is considered imaginary contract that sham, as permitted by law and what is not. Even though you will spend a large sum on the assistance of a lawyer, but to win your case, so you can get the benefit.
Use all possible evidence to prove your innocence. This can be witnesses of the transaction, security tapes and more. If you believe that you deliberately misled or you were not quite adequate, the witnesses will confirm this.
Expect a court decision on the recognition of the transaction null and void, and therefore invalid. The investigation will establish all the circumstances of the case, and if the contract is really concluded against the law, it will be recognized as non-existent.