Ontario construction liens: your 60-day preservation window (and why most claims die in it)

If you are a contractor, subcontractor, materials supplier, or equipment renter working on an improvement to Ontario real property and you are not being paid, the Construction Act (formerly the Construction Lien Act) gives you a remedy most other creditors would envy: the right to register a lien against the land itself.

It is a genuinely powerful tool. It also has some of the tightest deadlines in Canadian commercial law, and the vast majority of failed lien claims we see fail on timing — not on the merits.

Two deadlines, both fatal if missed

Under the modernized Construction Act (contracts signed on or after July 1, 2018), a lien claimant must:

• Preserve the lien within 60 days of the last day of the supply of services or materials to the improvement (or from publication of a certificate of substantial performance, for the general contractor).
• Perfect the preserved lien within 90 days of the same trigger date, by issuing a statement of claim and registering a certificate of action against title.

Preservation is done by registering a claim for lien on title. Perfection requires an action — the whole thing is not a paperwork exercise but a lawsuit with a very fast fuse. Miss either deadline and the lien is discharged automatically; you cannot revive it.

What 'last day of supply' actually means

The lien clock does not start on the invoice date or the date the owner stopped answering the phone. It starts on the last day you actually performed work or supplied materials to that specific improvement. Warranty work, punch-list items, and courtesy call-backs generally do not extend the period — a common trap.

If your last real supply was on a Tuesday in mid-May, count 60 days from that Tuesday and mark the calendar in red. Then count 90.

Prompt Payment and Adjudication — the softer track

Since October 2019, the Construction Act also imposes prompt-payment rules (28 days from a proper invoice on the top tier of the pyramid, cascading down) and offers interim adjudication as a fast, binding way to resolve payment disputes without going to court.

Adjudication runs on tight timelines (roughly 46 days end-to-end) and produces a determination that is immediately binding, subject to a court proceeding to finally resolve the matter. In many commercial files it is now the first serious escalation step, before or in parallel with lien enforcement.

Practical playbook when you're not being paid

• Confirm the last day of supply. Everything downstream depends on this date.
• Send a proper invoice under the prompt-payment rules — this starts the 28-day clock on the party you contracted with.
• If a payment dispute emerges, consider issuing a notice of adjudication early. It compresses the timeline and forces engagement.
• In parallel, get a lien opinion before day 45 of the 60-day preservation window. Do not wait until day 58.
• Assemble your evidence now: contract, change orders, delivery slips, dailies, correspondence. If a lien has to be registered, you will need it ready.

If you are inside the 60-day window and unsure whether to lien, book a short consultation — we can usually give you a lien-or-no-lien answer in one call. Beyond the lien question, an Ontario pre-litigation mandate can run in parallel: formal demand, adjudication where appropriate, and a decision point before you commit to a full action.

Bottom line

The Construction Act gives Ontario trades and suppliers real leverage — but only if you move on the calendar the Act sets. 60 days to preserve. 90 to perfect. 28 days per tier for payment. Miss one, and the strongest tool in your recovery toolbox disappears.