Subcontractors are generally required to provide invoices to their clients, which detail the work performed, the time spent on each task, and the total cost. This helps to ensure that both parties have a clear understanding of the work that was completed and the amount that is owed. Invoices also typically include information such as the subcontractor's name and contact information, the client's name and contact information, and any payment terms or conditions. It's important for subcontractors to keep accurate and detailed records of their work and to provide invoices in a timely manner to avoid any payment disputes or delays.