The answer to the seal of the purchase contract is that the purchase agreement does not need to be stamped with the official seal of the Housing Authority, but the signed purchase contract needs to be filed with the Housing Authority. 1. After the buyer confirms the purchase intention, the buyer and the seller jointly enter the formal contract terms into the contract filing software and sign the contract online through equal consultation. 2. After the house purchase contract signed by the developer and the property buyer is successfully reported, the formal (electronic) contract will be printed, and the property buyer and the developer will perform the signing procedures, and the number of copies to be printed will be determined according to the payment method (4 copies for one-time payment and 5 copies for mortgage loan). 3. Development enterprises need to go to the real estate transaction management department to handle the contract seal filing procedures within 3 working days after signing the contract online. After the online signing of the contract between the developer and the buyer is reported, the developer needs to bring all the purchase materials and a full set of signed (sealed) paper formal contracts to the competent real estate transaction management department to handle the contract seal filing procedures.