If the changed part is handwritten, you can apply to the court for identification, and judge whether it has been tampered with according to whether the writing time is consistent. If it is printed and tampered with, you can also apply for court appraisal. The copy of the contract is forged by signature, which constitutes contract fraud. According to the relevant provisions of the Civil Code, this contract is invalid and the handling fee is required to be returned. Signature can be used for handwriting identification. (1) Unilateral contract and bilateral contract. Unilateral contract refers to a contract in which only one party undertakes obligations. A bilateral contract refers to a contractual relationship in which both parties have the obligation to pay each other. (2) Paid contracts and unpaid contracts, paid contracts refer to contracts in which one party pays certain benefits to the other party by performing the obligations stipulated in the contract, and the other party must pay a corresponding price for such benefits. A gratuitous contract refers to a contract in which one party pays certain benefits and the other party does not pay any remuneration when obtaining benefits. (3) Well-known contracts and unnamed contracts Well-known contracts, also known as typical contracts, refer to contracts whose names and rules have been legally determined. Anonymous contract, also known as atypical contract, refers to a contract whose name and rules have not been determined legally. (4) Necessary contracts and non-essential contracts. A necessary contract refers to a contract that must be concluded in a special form as stipulated by law or agreed by the parties. Selective contract refers to a contract concluded without taking a specific form according to law. (5) Master contract and subordinate contract. A master contract refers to a contract that can exist independently of other contracts. Collateral contract refers to a contract based on the existence of other contracts, also known as collateral contract. A contract is an agreement between the parties to establish, change or terminate a civil relationship. Contracts established according to law are protected by law. A contract in a broad sense refers to an agreement in all legal departments to determine the relationship between rights and obligations. Narrow contract refers to all civil contracts. The narrowest contract only refers to the creditor's rights contract in civil contract. A contract, also known as a contract or agreement, is an agreement between equal parties to establish, change and terminate the relationship of civil rights and obligations. As a civil legal act, a contract is the product of the parties' agreement, and it is an agreement expressed by more than two parties. A contract is legally binding only when the meaning expressed by the parties is legal. A legally established contract shall take effect from the date of its establishment and be legally binding.