In Ontario a lien must generally be preserved within 60 days of the triggering event and perfected within a further 90. Any calendar can count that; the part that loses lien rights is establishing which date the clock started on.
Key takeaways
The arithmetic is the easy half. In Ontario a lien must generally be preserved within 60 days of the relevant triggering event and then perfected within a further 90 days, and any calendar can count that out. The hard half is establishing the trigger date, because that is a judgment about facts — and it is where lien rights are actually lost.
Treadstone Law states the rule plainly: a lien must generally be preserved within 60 days of the relevant triggering event, most commonly the last day services or materials were supplied to the improvement, or the date a certificate of substantial performance was published, whichever applies. Once preserved, the lien must then be perfected — a lien action started and the appropriate notice registered within a further 90 days following the last day it could have been preserved.
The Construction Act itself is more precise about the trigger than a summary can be, and the precision matters for a register. Section 31(2) provides that a contractor’s lien for services or materials supplied on or before the date of substantial performance expires at the conclusion of the 60-day period next following the occurrence of the earlier of the date a copy of the certificate or declaration of substantial performance is published, and the date the contract is completed, abandoned or terminated. Section 36(2) then fixes the perfection clock off that same reference point: a preserved lien expires unless it is perfected prior to the end of the 90-day period next following the last day, under section 31, on which the lien could have been preserved. Both counters key off the same section 31 event — which is exactly the register’s real design problem. Get the trigger wrong and the 60-day and 90-day fields are both silently wrong with it, not just one of them.
Miss either and the lien remedy for that claim generally ends, although the underlying contract debt can still be pursued in an ordinary action subject to the general limitation period. That nuance is worth knowing, because it explains why a missed lien deadline feels survivable and is nonetheless expensive: you have swapped a secured claim against land for an unsecured claim against a company.
A reminder system is only as good as the date it is counting from, and the date it counts from is a factual finding. Was the last attendance on site supply of services to the improvement, or a warranty visit? Did the small punch item that went back in March restart anything? Was a certificate of substantial performance published, and when?
The design consequence is specific: the trigger date must be a field that only a named person can set or change, with a note of why, and with an audit trail. Software can propose a candidate date from the daily log or the last invoice. It must not silently adopt it, because a system that quietly recalculates a deadline from a data change is worse than no system at all.
Two related judgments belong in the same place. Extras are a common source of confusion — our sister firm addresses whether extras and change orders count toward a lien claim. And lien rights run per contract along the chain, not per project, so a sub-subcontractor may have its own lien rights on its own timetable.
What a lien deadline register needs
One row per contract, not per project — each contractual relationship has its own clock.
A trigger-date field with an owner, a reason and a change history. Nobody else edits it.
Computed preservation and perfection dates, recalculated only when the trigger date is deliberately changed.
Escalating reminders that reach a person with authority, well before the date rather than on it.
A note of which version of the legislation governs the contract, recorded once at contract setup.
This trips up automated calculators. The Ontario adjudication authority records that there are four versions of the legislation that may apply to a construction project — the Construction Lien Act before 1 July 2018, the Construction Act as amended on 1 July 2018, as amended on 1 October 2019, and as amended on 1 January 2026 — with transition rules in the Act determining which applies, and it advises consulting a construction lawyer to work that out.
For a tracking system that means the governing version is a field captured once when the contract is set up, by someone who checked. A calculator that assumes the current rules apply to every contract in the book will be confidently wrong on the older ones.
Lien legislation is provincial, so a national contractor cannot run one rule. In British Columbia, the Builders Lien Act provides that where a certificate of completion has been issued, claims of lien may be filed no later than 45 days after the date the certificate was issued; where no certificate has been issued, the equivalent period runs from completion, abandonment or termination of the head contract.
That is a materially shorter window than Ontario’s, triggered by a different event, and it is the reason any multi-province register needs a province field driving the calculation rather than a single hard-coded rule.
Illustrative, and not a description of a real matter.
A mechanical subcontractor finishes a fit-out in April but returns twice in May to adjust a balancing damper. The bookkeeper, chasing an unpaid final invoice in July, asks whether a lien is still available. In a system where the last site attendance is auto-populated from the daily log, the answer displayed is reassuring and possibly wrong — whether those May attendances were supply of services to the improvement or warranty work is a legal question, and it moves the date by six weeks.
The version that works stores April as the proposed trigger, flags the May attendances for review, and escalates to the owner of the file in June rather than displaying a countdown nobody validated. The software’s job is to make sure the question is asked in time to answer it properly.
It can count days from a date you give it, and it can make sure the question reaches a person while there is still time. It cannot determine the triggering event, which depends on facts about the work and, sometimes, on documents published by others. Treat the output as a prompt to get advice, not as advice.
Not by itself. The clock runs from the triggering event, not from when the relationship broke down, which is why the deadline is so often discovered late — the dispute usually gets serious after the clock started. Set the register up at contract signature, not when payment goes quiet.
You may have lien rights of your own, running on your own contract. Our sister firm addresses that in a short note. The practical implication for the register is the same one as everywhere else in this article: rows are contracts, not sites.
A 30-minute call is enough to tell you whether AI pays for itself here.
