Legal analysis: After the additional down payment, the contract needs to be changed, because the purchase contract is for the bank, and the loan amount in the contract should be the same as the loan amount given to the bank. So you can sign a supplementary agreement with the bank to explain the situation in detail. First of all, it is necessary to determine whether the contract has been reported to the Housing Authority for the record. For those that have been put on record, within 3 working days after the signing of the commercial house, after negotiation between the buyer and the seller, it is necessary to change the relevant terms outside the core content of the contract, and the developer enterprise can read and revise the printed electronic contract again. If it has been filed for more than 3 working days, whether it is the core content or the content outside the core, the buyer and the seller reach an agreement through consultation and apply to the real estate transaction management department for contract filing and contract change.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 543 The parties may modify the contract through consultation.

Article 558 After the termination of creditor's rights and debts, the parties concerned shall abide by the principle of good faith and perform obligations such as notification, assistance, confidentiality, and recycling of old things in accordance with trading habits.

Article 559 When the creditor's rights and debts are extinguished, the subordinate rights of the creditor's rights shall be extinguished at the same time, except as otherwise provided by law or agreed by the parties.