The bid must be signed by the bidder to confirm that the result is valid. According to relevant information, the bid documents must be signed and sealed by the legal representative, otherwise the bid will be rejected. Bidding is a term in the bidding industry, which refers to the behavior that the tenderer (buyer) issues a tender notice or tender sheet in advance, puts forward the variety, quantity, technical requirements and related trading conditions, and invites bidders (sellers) to participate in bidding at the specified time and place.