How to File a Construction Lien in Ontario

Liens are a deadline game — start the clock in your head now

A construction lien is the Construction Act's security for people who improve land and don't get paid: contractors, subcontractors, suppliers of services or materials. It attaches to the owner's interest in the premises — which is exactly why the Act wraps it in short, unforgiving deadlines. Miss them and the lien right is gone, no matter how good the underlying claim is.

Two numbers matter more than everything else on this page: 60 and 90. You generally have 60 days to preserve the lien and a further 90 days after the last day it could have been preserved to perfect it. If you remember nothing else, remember to call a lawyer the week you stop being paid — not the week the deadline arrives.

Step 1 — Preserve the lien (generally 60 days)

Preservation means registering a claim for lien against the title of the premises (or, for certain public and municipal projects where liens do not attach to title, giving a copy of the claim to the right recipient). The 60-day period runs from triggers defined in the Act — for a contractor, typically the earlier of substantial performance being published or the contract being completed, abandoned or terminated; for subcontractors and suppliers, generally the date of last supply of services or materials.

The claim for lien states who you are, who you contracted with, what you supplied, the amount claimed, and a description of the premises. Errors here can be fatal or fixable depending on their nature — precision is cheap, litigation over sloppy claims is not.

Step 2 — Perfect the lien (the next 90 days)

A preserved lien expires unless it is perfected: you commence an action in the Superior Court of Justice to enforce it and, where the lien attaches to the premises, register a certificate of action on title. The perfection window is 90 days after the last day the lien could have been preserved.

Perfection is where self-represented lien claimants most often stumble — the lien claim was registered in time, and then nothing happened until it silently expired. Diarize both deadlines the day the problem starts.

The 10% holdback and why owners care

Owners (and each payer down the chain) must hold back 10% of the value of work and materials until the lien period expires. The holdback is the fund lien claimants look to first, and paying it out early does not defeat liens — it just exposes the payer to paying twice. Owners, keep the holdback until the clock runs out; claimants, know that this fund exists for you.

Prompt payment and adjudication — the faster track

Ontario's prompt-payment regime runs alongside liens: proper invoices are payable on a 28-day clock, non-payment requires a notice within strict timelines, and payment disputes can go to interim adjudication through ODACC (the Ontario Dispute Adjudication for Construction Contracts) while the project continues. For many disputes, adjudication gets money moving faster than a lien action — and preserving the lien in parallel protects the security.

Get the deadlines confirmed for your project

Which trigger starts your 60 days is a legal question that depends on your role in the chain and the facts of the project. Bring your contract, invoices and last-supply dates to a consultation — the first 15 minutes are free — and leave with your actual dates and a preservation plan.