During the engineering phase the owner of the property sold the property without any advance warning. They owe us money for engineering services and reimbursables for City fees. 1. Should the lien be filed against the original owner and property? I have the new owners information. 2. In the attachments should I include the invoice for the amount due as well as a copy of our contract, or just the invoice?
Liens are generally filed against the property owners, even if they are a third party that bought the property during the project. Liens only require you to have a general statement of the services you provided, so attachments are nice but not 100% necessary. If you have to sue to foreclose the lien (and probably sue for breach of contract too if warranted), then you'll include that contract and possibly invoicing as attachments to the court complaint.
Filing the lien is just a first step and most disputes stop there. If they don't respond to your lien, you'll need to talk to a construction attorney about how to recover the money from there.