Should I send a demand letter for an unpaid contractor invoice in Ontario?

Yes, a demand letter is almost always the right first step when a contractor's invoice goes unpaid in Ontario. A clear, professional letter sets out the amount owed, the services or work performed, and a reasonable payment deadline. It also creates a paper trail that supports your claim if you proceed to court or register a construction lien.

Ontario's Construction Act gives contractors, subcontractors, and suppliers the right to register a lien against the property where work was performed if they are not paid. Lien rights have strict timelines — generally, a lien must be preserved within a set number of days after the date of last supply of services or materials. You should not wait too long before acting. A demand letter is an important step, but it does not extend lien deadlines.

If the property owner or general contractor disputes the invoice or claims deficiencies in your work, get those concerns in writing so you can address them. Invoices, contracts, change orders, and written communications form the backbone of a construction dispute. Sending a demand before lien rights expire and before the limitation period runs keeps your options open.

A lawyer familiar with Ontario construction law can help you assess whether a lien, arbitration, or court claim is the best path after a failed demand.