Credit drawdown occurs when a customer uses credits from a pre-purchased balance to cover usage charges. The billing system tracks the remaining credit balance and automatically triggers notifications or re-purchase prompts when credits run low.

Example: A customer purchased 10,000 API credits in January. By March, they have drawn down 7,500 credits through API usage. The billing system alerts them when their balance drops below 2,000 credits, prompting a top-up purchase.