False Positive Rate (Fraud) is the percentage of legitimate transactions that your fraud system incorrectly flags or blocks as fraudulent.

Calculate it as: (Legitimate transactions flagged as fraud / Total legitimate transactions) × 100. Industry benchmarks vary wildly—aggressive systems see 5-10% false positive rates, while customer-friendly systems target under 1%.

False positives are where fraud prevention becomes a CX problem. Every declined legitimate transaction is a customer calling your support team, a cart abandonment, or a churned user. At scale, a 3% false positive rate on 1 million monthly transactions means 30,000 frustrated customers. Most of those customers won't call—they'll just leave.

The real cost isn't the support ticket. It's the lifetime value of customers who stop trusting your platform after a false decline at checkout or a frozen account during a legitimate purchase. Sophisticated fraud teams track false positive rates by customer segment, transaction size, and time of day to identify where their rules are too aggressive without exposing actual vulnerabilities.

Related terms: Fraud Detection Rate, Customer Effort Score, Transaction Approval Rate