What is considered permanent improvement/mechanic lien protection? We have Service Calls and Preventative Maintenance works for one owner. All properties locate at DC. The invoices the owner owe us include monthly Preventative Maintenance Agreement Billings, and individual Service Calls. Can we file mechanic lien for the unpaid invoices? How to consider these invoices as jobs when filing mechanic lien? i.e. Can all the unpaid service call invoices and monthly Preventative Maintenance Agreement billings for one single property be considered as one job to file one lien?