A Canadian contractor whose client refuses to pay the final invoice has four realistic options: send a formal demand letter, file a builders lien within the provincial deadline (typically 45 to 60 days after the work is finished), sue in small claims court, or sell the debt to a collection agency. Each option costs time and money, which is why most unpaid final invoices under $10,000 are simply written off.
Why the final invoice is the risky one
Once the work is delivered, the leverage flips. The client has the finished renovation, the completed landscaping, or the delivered project. You have an invoice. Nothing forces them to prioritize it, and "we are reviewing the invoice" can stretch for months.
Your options, in order of escalation
1. Formal demand letter
A dated letter stating the amount owed, the contract reference, and a payment deadline. Often enough for clients who are stalling rather than refusing. A lawyer-signed version costs $200 to $500 and carries more weight.
2. Builders lien
If you improved real property, every province gives you lien rights: Ontario gives 60 days from completion, Quebec's legal hypothec requires registration within 30 days, BC gives 45 days. A lien clouds the property title, which blocks refinancing and sales. It is powerful but slow, and enforcing it means going to court anyway.
3. Small claims court
Limits vary by province: $35,000 in Ontario, $15,000 in Quebec, $35,000 in BC. Filing costs are low but a contested case takes 6 to 18 months, and winning a judgment does not guarantee collection.
4. Collections
Agencies take 25 to 50 percent of anything recovered. Use this when you have given up on the relationship and just want something back.
The prevention answer
Every experienced contractor eventually converges on the same structure: deposits upfront, progress payments tied to milestones, and never letting the outstanding balance grow past what you can afford to lose. The gap is enforcement. A contract clause still requires you to chase the money after delivery.
The emerging alternative is milestone-based escrow: the client deposits the contract amount at the start, and payments release automatically as each agreed stage is approved. The final payment dispute never happens because the money was already committed before the work began.