An MC011 is eBay's request for additional documentation about your selling activity — typically triggered by rapid sales growth, new account activity, category changes, or risk flags. eBay usually requests supplier invoices, proof of inventory, tracking information, and business verification. Respond with organized, complete documentation — not partial records. Include an explanation of your business model, sourcing practices, and fulfillment process. Missing or incomplete documentation is the most common reason MC011 responses are rejected.