Advance payment guarantee, also known as repayment guarantee and refund guarantee, can also be a deposit guarantee in a trade contract. In the large transaction of engineering contracting, material procurement and other projects, the buyer or owner needs to pay a certain proportion of money to the supplier in advance within a certain period of time after the contract is signed as the start-up fund for contract execution. Because the money was paid to the supplier in advance before the performance, the buyer avoided the unreasonable losses caused by the supplier's refusal or inability to perform the obligations in the future, and did not refund. Usually, the supplier is required to issue an advance payment guarantee through his bank a few days before the buyer advances the payment. Some banks promise that once the applicant fails to perform the contract or fails to fully perform the contract (whether intentionally or unintentionally), after receiving the buyer's claim, the guarantee bank will return the amount equivalent to the prepayment amount or a considerable proportion of the prepayment amount equivalent to the unfulfilled part of the contract to the buyer, so that the buyer can recover the prepayment amount smoothly. Advance payment guarantee is used to apply for advance payment from the owner, and the guarantee period is up to a certain node of the project.