Which of the following is required to set up an invoice list?

The requirement to define a factory calendar and assign it to the customer master of the payer is essential for setting up an invoice list because it ensures that the invoicing process aligns with the operational schedule and specific business days of the company. The factory calendar includes information about working days, holidays, and other non-working periods that can affect when invoices are issued and processed. Assigning this calendar to the customer master helps automate billing processes and ensures that invoices reflect accurate timing concerning the customer's payment cycles and the company's policy on payment deadlines.

A factory calendar enables the system to consider these factors when generating invoice lists, ensuring timely and accurate invoicing in accordance with predefined schedules. Proper assignment of the factory calendar also minimizes issues related to invoicing and payment delays, fostering a smoother transactional experience for both the company and its customers.

The other choices focus on different aspects of invoice management, but they do not directly relate to the foundational setup necessary for creating an invoice list within the relevant timeframe guided by a factory calendar.