Bid rigging can take several forms, including bid suppression, complementary bidding, bid rotation, and subcontracting. In bid suppression, some bidders agree not to submit a bid, ensuring a pre-selected bidder will win. Complementary bidding involves submitting intentionally high bids or bids with unacceptable terms to give the appearance of competition. In bid rotation, competitors take turns being the winning bidder on a series of contracts. Subcontracting occurs when the winning bidder agrees to subcontract parts of the work to losing bidders as a reward for their compliance.