The contract on estimate (art. 2107 Civil Code of Quebec)  

The contractor must justify any increase in the cost of the contract

The fixed price contract (art. 2109 Civil Code of Quebec):

 The agreed price must be paid without increase or decrease due to the actual cost of the work, with exceptions - extras

The "cost plus" contract (art. 2108 Civil Code of Quebec)

At the request of the client, the contractor must report the actual cost of the work and its progress, to which is added the "cost plus" in the form of a percentage