In British Columbia, the right to file a claim of builders lien is powerful and perishable. File in time and you have security against the land itself for what you're owed. Miss the window and the right is gone entirely, no matter how good your claim is.
The window is 45 days. What trips people up is not the number, it's knowing when the clock starts.
What starts the 45-day clock
Under section 20 of the Builders Lien Act, the clock starts on the earlier of two triggers. If a Certificate of Completion is issued for the contract or subcontract under which the lien arises, you have 45 days from the date of that certificate. If no certificate is issued, you have 45 days from the date the head contract is completed, abandoned, or terminated.
The Certificate of Completion trigger is the one that catches subcontractors. A certificate can be issued for your subcontract while the overall project runs for months longer. Your lien window closes 45 days later even though everyone is still on site. If you don't know a certificate was issued, your clock is running and you can't see it.
A payment certifier who receives a written request must determine whether a contract is substantially performed and, if so, issue the certificate within 10 days. Owners and contractors use this to start lien clocks deliberately. Treat any completion certificate on any contract in your chain as a live deadline.
What filing actually means
Filing means registering the claim of lien in the land title office against the land being improved, in the prescribed form, before the deadline. Not mailing it, not telling the GC you intend to, not a lawyer's demand letter. If the 45th day is approaching and you are owed money, get the filing done; you can always discharge a lien later, but you cannot late-file one.
After filing, a second deadline starts: under section 33, you must start an action to enforce the lien and register a certificate of pending litigation within one year of filing, or the lien expires.
How to stay ahead of it
Track two dates on every project: whether a Certificate of Completion has been issued on your contract or any contract above you, and the status of the head contract. When either trigger fires, calendar day 45 immediately and decide well before then whether you're filing.
LienClock's free calculator does the date math for you, and the tracker (launching soon) watches every project and alerts you before the window closes.