Missing Level 3 card data cost a B2B marketplace 180bps in extra fees

A B2B marketplace discovered its payment integration was submitting only basic Level 1 card data — cardholder number, amount, and date — instead of the richer Level 2/3 fields required for lower interchange rates on commercial cards. Without fields like tax amount, PO number, and line-item details such as SKU and commodity codes, every affected transaction was automatically downgraded to the standard commercial interchange rate. The gap proved costly: transactions with full Level 3 data settled at roughly 1.8% effective rate, while those without it settled near 3.6% — a difference of about 180 basis points on six-figure monthly volume. The issue was resolved by making tax amount and PO number mandatory before authorization and pulling existing line-item data from the order database. The effective rate on new transactions fell within a single billing cycle after the fix was applied.