Here's an interesting case that may enlighten, however it was approached as a consumer contract because it was not onerous. https://www.canlii.org/en/qc/qccs/doc/2011/2011qccs1506/2011...

How onerous is it to be forced to use CRA online services ? Are the taxes you pay considered onerous ? Are the CRA TOS considered an adhesion contract ?

This should really be tested by by the justice system rather than enthusiasts on a discussion forum. However, since we're all governed by such laws, it's never a loss to spend time on learning about them, especially physics.

1378. A contract is an agreement of wills by which one or several persons obligate themselves to one or several other persons to perform a prestation. Contracts may be divided into contracts of adhesion and contracts by mutual agreement, synallagmatic and unilateral contracts, onerous and gratuitous contracts, commutative and aleatory contracts, and contracts of instantaneous performance or of successive performance; they may also be consumer contracts.

1379. A contract of adhesion is a contract in which the essential stipulations were imposed or drawn up by one of the parties, on his behalf or upon his instructions, and were not negotiable. Any contract that is not a contract of adhesion is a contract by mutual agreement.

1384. A consumer contract is a contract whose field of application is delimited by legislation respecting consumer protection whereby one of the parties, being a natural person, the consumer, acquires, leases, borrows or obtains in any other manner, for personal, family or domestic purposes, property or services from the other party, who offers such property or services as part of an enterprise which he carries on.