A sub-tier is any subcontractor (for example, a subcontractor, supplier, or vendor) who furnishes materials, supplies, or services connected to the first-tier subcontractor's obligations on a commitment. In Procore Pay, a first-tier subcontractor is the 'Contract Company' who enters into a commitment contract with a General Contractor. Both first-tier and sub-tier contractors might hire additional sub-tiers (for example, third-tier, fourth-tier, and so on).