Mechanic's liens only apply to improvements to real property or buildings/structures. So if the repairs were to a vehicle, you cannot file a mechanic's lien. If you are in possession of the vehicle, then you can assert what is called a garage lien on the vehicle, which allows you to keep possession of the vehicle until you are paid. If you do not have possession of the vehicle, you can still sue for the money owed either by breach of contract or unjust enrichment (if there is no contract). The absence of a written contract does not mean that there is no contract. Oral contracts are enforceable.