What is required for a tradesman to file a lien?

[Elliot Cole]

Long story short, my wife and I have a condo where a terrible plumbing company botched a water heater replacement, caused a lot of subsequent damage, failed the city inspection, then demanded payment in full. We never had a written contract and they haven’t provided us an invoice, yet the project has not been very friendly and they filed a Notice to Lien on us. With 15 days to go on the notice, is this a scare tactic or can they legitimately file a lien at the end of the 15-day period when no contract or invoice has been signed or provided?