1. If an invoice includes both the supply of materials and services, and the value of the materials and services is mentioned separately, then TDS will be calculated separately on the value of the materials and on the value of the services.
2. If the invoice includes a supply of materials and services, but the value of the materials and services is not mentioned separately, then TDS will be calculated on the total value of the invoice.
In both cases, the TDS liability will be calculated under Section 194C of the Income Tax Act of India, which relates to TDS on payments made to contractors and professionals.