Whether the contract is sealed by Party A or Party B depends on the situation. The details are as follows: there is no law in the contract stipulating whether the contract should be sealed by both parties or only one party. Both sides are free to choose. The purpose of suing for sealing a contract is to prevent one party from amending the contract, and there is no special provision in law on whether it is necessary to seal it.

The contract seal is a seal stamped at the document handover to ensure the integrity of the documents retained by the goods and help to verify the relevant documents. Every page of the contract should be stamped with a red seal to ensure that the first and last pages of the contract are printed with the words on the seal, and there are no missing pages in the contract.

The purpose of the contract seal is to prevent contract risks for enterprises. After the enterprise stamps the riding seal, the whole contract will restore the riding seal to the original seal, which can prevent the other enterprise from changing and denying the contract content, effectively ensure the normal development of the enterprise's business activities, and thus promote the expansion of the enterprise's business.

The riding seam stamp refers to pressing the edge seam when stamping. That is, the official seal should be evenly covered on the middle seam of two foldable papers, half of which should be kept as a stub and the other half as a voucher. When verifying, the two halves should be opposite and the official seal should be complete. When affixing the riding seal, all joints should be affixed with the riding seal, that is, after affixing the riding seal, each page of the contract should have a red seal, and it is best that the first page and the last page have words at the same time, not just a red circle. In addition, whether it is a red circle is easy to cheat.

Article 490 of the Civil Code of People's Republic of China (PRC): If the parties conclude a contract in the form of a contract, the contract is concluded when the parties sign, seal or fingerprint it. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it.

A contract shall be concluded in written form as stipulated by laws, administrative regulations or agreed by the parties. If the parties do not do this in writing, but one party has fulfilled its main obligations and the other party accepts it, the contract is established.