How much time does a contractor have to register a lien after finishing work in Ontario?

Under the Construction Act, a lien must generally be preserved - meaning registered against the property's title, or otherwise preserved as the Act permits - 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 to your situation. This 60-day window is calculated strictly, and it's one of the most common ways lienholders lose their remedy entirely - waiting even a short time past the deadline, believing there's still room, is a frequent and costly mistake.

Once a lien is preserved within that window, it must then also be "perfected" - meaning a lien action is started in court and the appropriate notice is registered - within a further 90 days following the last day the lien could have been preserved. Missing either deadline generally ends the lien remedy for that claim, though it doesn't necessarily end the underlying contract claim for the debt itself, which can still be pursued through an ordinary lawsuit subject to the general limitation period. Given how unforgiving these deadlines are, tracking the exact trigger date as soon as a payment dispute looks likely is essential.