Contract B is a concept in Canadian law. A Contract B is formed when an Owner formally accepts a Bid or, colloquially, a submission of price. Only a single Contract B is formed between the Owner and the successful bidder. Tied to the concept of Contract A, Contract B is a place holder in the concept, a marker at the end of a formalized process of equitable treatment of both bidders and owners. In many ways it is more of an academic detail within the Contract A - Contract B concept, but can also be thought of as a label for the actual construction contract.
References
Contract B Wikipedia(Text) CC BY-SA