A lien is a legal claim against property that secures payment of a debt or obligation. In construction, contractors and suppliers who provide labour or materials can register liens against properties if they are not paid, preventing sale or refinancing until the debt is settled. Municipalities also place liens on properties for unpaid property taxes, utility charges, or special assessments, ensuring these debts are collected when the property sells. Liens are registered against property titles and remain attached regardless of ownership changes. Understanding liens helps property owners, contractors, and municipalities protect their financial interests and resolve payment disputes.