Which practice is a timeshare sales agent prohibited from doing regarding credit cards?

The practice that a timeshare sales agent is prohibited from doing regarding credit cards is retaining them beyond necessary checks. This prohibition is in place to protect consumers' financial information and privacy. When a sales agent processes a transaction or verifies a payment method, they only need to retain the credit card details for as long as is absolutely necessary to complete that specific interaction. Holding onto credit card information longer than required increases the risk of unauthorized access or potential misuse, which raises significant ethical and legal concerns.

By limiting the retention of credit card information, regulations aim to minimize the potential for fraud and identity theft, ensuring that consumers can trust the entities they engage with. This practice also aligns with best practices in data protection and privacy laws that govern how sensitive information should be handled.

In other options, while they may touch upon issues of consent and security, they do not encapsulate the core regulatory guideline surrounding the retention of credit card information as effectively as the correct answer does.