Is a cohabitation agreement actually enforceable in Ontario courts?

Yes, a properly made cohabitation agreement is legally binding and enforceable under Ontario's Family Law Act. To be valid, it must be in writing, signed by both parties, and witnessed. However, courts have the authority to set aside a domestic contract, or parts of it, in certain circumstances.

Grounds for setting aside an agreement include: a party failed to disclose significant assets or debts before signing; a party did not understand the nature or consequences of the agreement; one party was under duress, undue influence, or there was unconscionability in how the deal was reached. Courts have also set aside clauses that attempt to deal with matters the Family Law Act says cannot be contracted out of, such as child support obligations.

The most common reason agreements fail in court is that one or both parties lacked independent legal advice. When each party has their own lawyer review the agreement before signing, it is much harder to later claim they did not understand what they signed. Full financial disclosure before signing is equally important. A well-drafted agreement negotiated transparently and with legal advice on both sides has the best chance of surviving a challenge years later.