Understanding Liens

Any contractor, subcontractor or material supplier for a building project may file a mechanic's lien on the property they worked on if they are not paid for their labor or materials contribution.  Minnesota law provides a number of procedures and conditions that protect homeowners from being the target of an unfair mechanic's lien, though only a court can determine whether a lien is valid.  In most cases, a contractor must provide written notice of intent to file a lien if the contractor is not paid.  This notice is required whenever subcontractors or material suppliers are employed.

-Minnesota Dept. of Labor and Industry
  "A Consumer's Guide to Hiring a Contractor "