Construction Liens in Ontario: How to Register and Protect Your Claim

You finished the work. You submitted your invoice. And now the owner, general contractor, or developer is delaying, disputing, or simply not paying. If this sounds familiar, you may have the right to register a construction lien Ontario law provides — a powerful legal tool that can attach directly to the property you improved and force the people above you in the payment chain to take you seriously.

Ontario's Construction Act gives contractors, subcontractors, suppliers, workers, and other contributors to a construction project a statutory right to register a lien against real property as security for unpaid amounts. That right is meaningful, but it comes with some of the strictest and most unforgiving deadlines in Ontario law. Miss them — even by a day — and the lien right is lost, often permanently.

This article explains what a construction lien is, who can register one, how the registration process works, and why getting legal advice early is not a luxury but a practical necessity.

What Is a Construction Lien?

A construction lien (called a "claim for lien" under the Construction Act) is a legal charge registered against the title of real property. It gives an unpaid person who contributed labour, materials, or services to the improvement of that property a security interest in the land itself — similar in some ways to a mortgage, except it arises by operation of statute rather than by contract.

The purpose is straightforward: it prevents an owner from selling, refinancing, or dealing freely with the property until the unpaid claim is resolved. It also puts every person in the payment chain — owners, lenders, general contractors — on notice that money is owed and that the claimant is not going away quietly.

Unlike a standard breach-of-contract claim where you sue and hope the defendant has assets to pay a judgment, a lien is attached to something that almost always has real value: the land and everything built on it.

Who Can Register a Construction Lien in Ontario?

The Construction Act casts a wide net. As of writing, the following categories of person generally have lien rights (verify your specific situation with a lawyer):

• General contractors and prime contractors hired directly by the owner
• Subcontractors hired by the general contractor
• Sub-subcontractors and further tiers of subcontracting
• Suppliers of materials incorporated into the improvement
• Workers who performed labour on the project
• Architects, engineers, and other design professionals who provided services in connection with the improvement
• Lessors of equipment used on the project (subject to specific conditions)

The key question is whether you "supplied services or materials to an improvement." If you contributed something that made the property better, there is a reasonable chance you have lien rights — but the details matter, and marginal cases require legal analysis.

What Property Does a Lien Attach To?

A construction lien attaches to the owner's interest in the land being improved. This is important: the lien runs with the property, not with the person who owes you money.

If the person who hired you is a general contractor rather than the owner, your lien still attaches to the owner's land — even though you have no direct contract with the owner. This is one of the most powerful features of construction lien law. The owner's property becomes security for debts owed by people further down the payment chain.

There are nuances:

• If the land is owned by the Crown (federal or provincial government), or a municipality, lien rights work differently. Public-sector projects are governed by separate holdback and trust provisions — speak with a lawyer about these.
• If the improvement is to a leasehold interest (a tenant's lease), the lien may attach to the lease rather than the fee simple title.
• The lien attaches to the owner's interest as of the date the lien is registered, not the date the work began.

How Construction Lien Registration Works: A Step-by-Step Overview

Registering a lien is not a casual administrative task. Each step has legal significance and potential pitfalls.

1. Determine the last date you supplied services or materials. This is the starting point for calculating your deadline. It is not the date of your invoice or the date payment was due — it is when you last contributed work or materials to the project.

1. Calculate the lien deadline. As of writing, most lien claimants have a set number of days from the date of last supply to register their lien — verify the current period with a lawyer immediately, as this deadline is absolute. There is also a separate deadline triggered by the publication of a Certificate of Substantial Performance (a formal document published when the project reaches a defined completion threshold). Whichever deadline applies to you, missing it extinguishes your lien right.

1. Prepare the claim for lien. The lien document must meet specific formal requirements under the Construction Act, including the correct legal description of the property, the amount claimed, and the name of the owner. Errors in the document can invalidate the lien.

1. Register the lien on title. Lien registration is done through the Ontario land registry system (Teraview). The lien must be registered before the deadline expires — not submitted, not mailed, but registered.

1. Preserve the lien by commencing an action. Registration alone is not enough. Within another set deadline after registration, you must commence a court action (or, in some cases, an arbitration) to enforce the lien. If you do not take this step in time, the lien is deemed to have expired and can be discharged.

1. Perfect the lien at trial. Ultimately, to collect, you must obtain a court judgment that declares the lien valid and orders the property sold or the lien enforced. This is the litigation phase.

The Holdback: Why Owners Are Required to Keep Money Back

The Construction Act requires owners to hold back a percentage of each progress payment made to a contractor (as of writing — verify the current percentage). This statutory holdback exists precisely to provide a fund that lien claimants can look to. It is not optional. An owner who fails to maintain the holdback can become personally liable to lien claimants who go unpaid.

If you are a subcontractor or supplier, you have rights against the holdback even though it is held by the owner. Understanding how the holdback works — and how to make a claim against it — is a core part of exercising your lien rights effectively.

Why Deadlines Are the Most Important Thing to Understand

Construction law practitioners in Ontario will tell you the same thing: **the deadlines under the Construction Act are among the harshest in all of civil litigation.** Courts have very little discretion to extend them. An expired lien right is not a procedural inconvenience — it is a lost right, full stop.

The deadline calculation is also not always obvious. Questions such as when "last supply" occurred, whether certain warranty work or punchlist items restart the clock, and whether a Certificate of Substantial Performance was properly published can all affect your deadline. These are not questions to work out on the day the deadline arrives.

If you are owed money on a construction project and you believe payment may not be coming, the single most important thing you can do is speak with a construction litigation lawyer immediately — before you assume you have more time than you actually do.

Frequently asked questions