Correct Option: C. Dealing regularly with a customer Explanation of Why Option C is Correct: A pro forma invoice is a preliminary bill of sale that outlines the details of a transaction before the actual sale occurs. It is often used to provide a quote to a buyer, to outline the terms of sale, or to facilitate customs clearance for international shipments. However, when a business is dealing regularly with a customer, the need for a pro forma invoice diminishes significantly. Here’s why:

1. Established Relationship: When a business has an ongoing relationship with a customer, both parties are familiar with the pricing, terms, and conditions of their transactions. This familiarity reduces the need for a pro forma invoice, as the customer can trust that the final invoice will reflect the agreed-upon terms.
2. Streamlined Process: Regular transactions often lead to streamlined processes where the seller can directly issue invoices without needing to provide a pro forma invoice first. This saves time and resources for both the seller and the buyer.
3. Trust and Reliability: In a regular business relationship, there is a level of trust established. The customer is likely to be confident in the seller's pricing and product quality, making the pro forma invoice unnecessary.

Why the Other Options are Wrong or Weaker: A. Quoting for the supply of goods - Explanation: A pro forma invoice is often used when quoting for the supply of goods. It provides a detailed breakdown of costs, terms, and conditions, which helps the buyer understand what they are agreeing to. Therefore, this option is incorrect because a pro forma invoice is indeed required in this scenario. B. Goods are sent on approval - Explanation: When goods are sent on approval, a pro forma invoice may still be necessary to outline the terms of the approval process, including pricing and return conditions. This ensures that both parties are clear on the expectations and responsibilities. Thus, this option is also incorrect. D. Final prices are uncertain - Explanation: If final prices are uncertain, a pro forma invoice can help clarify potential costs and terms before the final sale is made. It serves as a way to communicate estimated prices and conditions, making this option incorrect as well. Summary of Key Points:

• A pro forma invoice is not needed when dealing with regular customers due to established trust and familiarity.
• It is essential for quoting, sending goods on approval, and when final prices are uncertain.
• Regular transactions streamline the invoicing process, eliminating the need for preliminary documents.
• Understanding the context of transactions helps determine when a pro forma invoice is necessary.