If a customer in Ontario has stopped paying you on a construction project, the most powerful tool you have is a construction lien. Filed correctly, it stops the owner from selling or refinancing the property without dealing with your claim. Most owners pay within weeks of a lien being registered, because the alternative is having the lien sit on title indefinitely.

But Ontario’s lien rules are unforgiving. Miss the 60-day preservation deadline and the right is gone permanently. Miss the additional 90-day perfection deadline and the right is gone even if you registered the lien in time. This guide walks through both steps in plain language, with section references to the Construction Act so you can confirm each rule against the statute.

For deadlines outside Ontario, see the province-by-province lien deadline guide or the free multi-province lien deadline calculator.

When you can file a lien in Ontario

The Construction Act gives lien rights to anyone who supplies services or materials to an improvement of land in Ontario. That includes general contractors, subcontractors, suppliers, equipment rental companies, and workers. It does not require a written contract; verbal contracts give rise to lien rights too, although they are harder to prove.

The lien attaches to the owner’s interest in the land where you did the work. If the owner does not own the land outright (for example, on a long-term commercial lease), the lien only attaches to whatever interest the owner has. For most residential and small-commercial work, the owner is the freehold owner and the lien attaches to the full title.

Step 1: Preserve the lien (60-day deadline)

Preservation means filing a claim of lien on title at the Ontario Land Registry Office for the registry division where the land is located. You must do this within 60 days of the earliest of:

  • publication of a Certificate of Substantial Performance (CSP), or
  • completion, abandonment, or termination of the contract, or
  • (for subcontractors) the last day on which you supplied services or materials.

This 60-day window is set by section 31 of the Construction Act. The deadline is calendar days, not business days, and is calculated from the trigger date itself. The deadline was 45 days under the pre-2018 Construction Lien Act; if any older template or article says 45 days for Ontario, it is out of date.

The form: Claim for Lien (Form 12)

The lien claim is filed as Form 12 (Claim for Lien), prescribed by O.Reg 303/18 under the Construction Act. Section 34 of the Act specifies what must appear on the form:

  1. The claimant’s name and address.
  2. The owner’s name and address.
  3. The date of the contract or subcontract and the names of the other parties.
  4. A short description of the services or materials supplied.
  5. The contract price or sub-price, or its value if unstated.
  6. The amount claimed as owing.
  7. A description of the premises (the legal land description, not the street address).
  8. The date the work was last performed.

The legal land description (PIN, plan, lot, and concession) is critical. A street address alone is not sufficient. You can pull the PIN from a title search or from any prior registration on the property. A real-estate lawyer can run this for you for a small fee, or you can use Teraview directly if you have a subscription.

Where to file: Teraview, not paper

Since October 11, 2016, lien registrations in Ontario must be filed electronically through Teraview. Paper filings at the Land Registry Office are no longer accepted. Teraview is the same electronic platform real-estate lawyers use to register mortgages and transfers, so most contractors retain a lawyer or paralegal who already has a subscription.

Filing a lien yourself through Teraview is technically possible but requires a subscription, an account, and familiarity with the document-preparation workflow. For a one-off lien on a single property, retaining a construction or real-estate lawyer for the registration step typically runs $300 to $700 plus the government-set Land Titles registration fee. Confirm the current registration fee on the Teraview fee schedule before filing.

Serving the owner

After registering the lien on title, you must serve a copy of the lien claim on the owner. The Act does not impose a strict deadline on service, but practical wisdom is to serve within the same week as registration. Service can be by personal delivery, mail, or any method permitted by the Rules of Civil Procedure. Keep proof of service; you will need it at the perfection stage.

Step 2: Perfect the lien (90-day deadline)

Preservation is only step one. To enforce the lien, you must perfect it within 90 days after the last day on which the lien could have been preserved (section 36). Perfection requires two things to happen within that 90-day window:

  1. Commence a court action against the owner (and anyone else liable for the amount, including the GC if you are a sub). The action is started by issuing a statement of claim in the Superior Court of Justice in the region where the land is located.
  2. Register a Certificate of Action on title against the property. The certificate is also filed electronically through Teraview and serves as notice to the world that the lien is being actively pursued.

Missing the 90-day perfection deadline extinguishes the lien even if it was registered on time. Many liens die at this stage because contractors register the lien themselves and then assume the work is done. It is not.

What the owner can do (and what you should expect)

Once a lien is registered, the owner has three realistic options:

  1. Pay the amount. This is the most common outcome on residential and small-commercial projects. The owner cannot sell or refinance while the lien is on title, so most pay quickly rather than fight.
  2. Vacate the lien with security. Under section 44 of the Act, an owner can post security (cash or a lien bond) equal to the amount of the lien plus 25% for costs (the latter capped at $250,000). When security is posted, the lien is removed from title but continues against the security. This is common on commercial deals where the property must be saleable.
  3. Dispute the lien. The owner can argue the lien is invalid for procedural reasons (wrong amount, wrong land description, late filing) or for substantive reasons (the work was deficient, the contract was breached). This is the path that requires both sides to litigate.

On the majority of valid liens for small-business contractors, outcome 1 or 2 happens within 30 to 60 days of registration. The leverage created by having a lien on title is, in practice, the whole point.

What it costs you

The Land Titles registration fee is set by regulation and adjusted roughly half the rate of inflation every year. The current 2026 amount changes with each adjustment; confirm against the Teraview fee schedule or a service-provider quote before filing. On top of the government fee, a construction or real-estate lawyer typically charges $300 to $700 to prepare and register a single lien (more if multiple properties or claimants are involved).

Perfection is a separate cost. Commencing a Superior Court action and registering a Certificate of Action typically runs $1,000 to $3,000 in legal fees plus the court filing fee, depending on the complexity of the claim. For lien claims under $35,000, the matter may proceed to Small Claims Court instead, which is cheaper.

Five common mistakes that kill liens

  1. Citing the wrong deadline. The preservation window is 60 days, not 45. The 45-day figure is left over from the old Construction Lien Act.
  2. Using a street address instead of a legal land description. Form 12 requires the PIN, plan, and lot numbers. A street address is not enough.
  3. Inflating the lien amount.Section 35 of the Act imposes liability for inflating a lien claim “wilfully or with gross negligence.” Claim only the amount you can document.
  4. Forgetting the perfection step. Registering the lien on title is only step one. You have 90 days after the preservation window to commence a court action and register a Certificate of Action. Many liens die here.
  5. Filing too late. The 60-day clock is calendar days from the earliest trigger event. If you supplied materials weekly for two months and stopped 65 days ago, the lien is already extinguished.

This article is general information for Ontario trades contractors, not legal advice. Filing a lien correctly requires attention to details: wrong amounts, wrong land descriptions, and missed deadlines all kill liens. Before filing, retain a construction or real-estate lawyer licensed in Ontario. Markup is a software platform, not a law firm.