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Fraud-scoring procedures are used to identify the highest-risk transactions that require additional verification. The result is presented as a score that provides the probability that a transaction may be fraudulent. ECommerce merchants should develop internal transaction fraud-scoring procedures or utilize third-party services to do that for them. The following best practices should be followed for best results:
Web-based merchants should perform internal fraud screening before submitting transactions for fraud scoring. When submitting transactions for fraud scoring, consider the following suggestions:
Only submit transactions that have passed your organization’s internal fraud screening procedures. Transactions that have failed are obviously high-risk and you do not need their fraud score to indicate that.
You should not obtain fraud scores for transactions that were declined by the card issuer or have raised flags for suspected fraud or other reasons.

Online merchants should evaluate the costs and benefits of fraud scoring for low-risk transactions. For many merchants it will not be cost-effective to obtain fraud scores, internal or third-party, for every single eCommerce payment transaction. Eliminating the low-risk transactions from the fraud-scoring process will help keep costs down.

If using third-party scoring, merchants should analyze their service agreements and estimate the cost of submitting transactions to them.
Merchants should identify transactions where the potential fraud losses are lower than the cost of fraud scoring. The following factors should be taken into account when making the decision:
Total dollar amount of the sale.
Whether it is a new or repeat customer.
Type of service or product being sold.
The eCommerce website’s click-through patterns.
Address Verification Service results.
Card Security Code results.
Verified by Visa or MasterCard SecureCode results.