To have a valid separation agreement in Ontario, you have to meet three basic criteria: the agreement has to be in writing, it has to be signed and both parties have to have their signature witnessed.
There are some additional considerations. A court can set aside the agreement, if either party asks, in certain conditions. These additional conditions essentially create other rules you must follow. Those rules are:
1) Both parties have to fully understand the agreement – to understand a legal document judges think people should have independent legal advice, so this really means both sides need to see a lawyer to at least have the agreement explained to them before they sign.
2) The parties must exchange all relevant financial disclosures. This usually means exchanging information about your income, all your assets (and their value) and all of your debts. This goes back to understanding again. How can you understand if your deal is a good one if you do not know what your ex’s financial situation is like?
24 – How to Have a Valid and Enforceable Separation Agreement
3) The agreement must otherwise comply with the law of contract. There are rules for contracts. Lawyers know them. You would probably have to get a book on contract law to know them. Also, complying with the law of contract also means that the negotiations were done properly and the parties fully contemplated their circumstances at the time of the agreement and in the future. Again, the best way to make sure you have done this is to see a lawyer.