Can what I write in a demand letter be used against me in court in Ontario?

Yes, anything you write in a demand letter can potentially be used as evidence in court proceedings. A demand letter is not protected by any automatic privilege. If you make factual concessions, admit fault, miscalculate your damages, or use inflammatory language, the other side can introduce your letter as evidence.

This is one of the key reasons to be careful — or to have a lawyer draft the letter. Demand letters should stick to accurate factual statements and the specific remedy you are seeking. Avoid speculation, admitting partial liability if you are not fully at fault, exaggerating losses, or making threats that could constitute extortion or defamation.

If you wish to communicate settlement proposals in a way that prevents them from being used as evidence, you can mark the communication "Without Prejudice." Under Ontario civil procedure, without-prejudice communications made for the purpose of settling a dispute are generally protected from being admitted as evidence of liability. However, the rule has nuances and exceptions. A demand letter asserting your claim and demanding payment is typically not a without-prejudice document — it is a formal assertion of your position. A lawyer can help you structure your communications to protect your interests while still putting the other side on notice.