1. What is the payment method for the tender documents? Can the method of payment be changed? Why?

The mode of payment in the bidding documents and the contract must be consistent with the agreed mode of payment, the mode of payment can not be changed. Article 46 of the bidding law: the bidder and the successful bidder shall, within thirty days from the date of issuance of the notice of award, in accordance with the bidding documents and the bidding documents of the successful bidder to enter into a written contract. The bidder and the successful bidder shall not enter into any other agreement that departs from the substance of the contract. Since it is the winning bidder has won the bid, it means that the bidding documents of the winning bidder are the most in line with the requirements of the bidding documents and are acceptable to the bidder. Then, the bidder and the successful bidder should sign a contract based on the bidding documents of the successful bidder, which naturally includes the payment method. If the actual signing of the contract, the payment method is changed, that is, the bidding documents are changed, is not in line with the above law. Article 30 of the Contract Law stipulates that the content of a promise shall be consistent with the content of an offer. If the offeree makes substantial changes to the content of the offer, it is a new offer. Changes relating to the subject matter of the contract, quantity, quality, price or remuneration, period of performance, place and manner of performance, liability for breach of contract and method of dispute settlement are substantive changes to the content of the offer. Although the payment method is not explicitly included in the substantive content, but on the longer period and the cost of capital to the winning bidding project, the payment method of change will have a direct impact on the change of the bid price, and will affect the legitimate rights and interests of the third party (i.e., unsuccessful bidder) and lead to unfairness, so for this type of bidding, the payment method should be considered as a substantial part of the content and shall not be changed.