The short answer
In addition to the main 22-character billing descriptor, the card networks allow a second 13-character field originally meant for the merchant's city and state. Most modern processors (Stripe, Adyen, Braintree) let you populate it with anything — which means you can use it as a support phone number or a short URL.
In plain English
Open your own credit card statement and look at any charge. You'll see something like SUNRISEBOTAN*VITAMINS 888-555-0101 CA. The first block is the billing descriptor. The "888-555-0101 CA" is the city/state field. Every dollar you spend on fraud tools is undone if a customer can't tell what a charge was for. A visible support phone number in this field is the cheapest chargeback-prevention tool in existence.
What operators need to know
- 13 characters max — exactly enough for a 10-digit phone with dashes (888-555-0101) or a short domain (buy.brand.co).
- Per-processor rules vary — Stripe exposes `statement_descriptor_suffix` for the second field on some products; Adyen has a full "City" param.
- Phone number wins over URL in dispute studies — customers call the number and you resolve live instead of losing to a chargeback.
- Must be reachable — staff the number. A dead phone line in the descriptor is worse than no phone line.
- Per-brand values — route each brand's charges to that brand's support line, not a central call center.
Numbers to know
Merchants who populate the city/state field with a live phone number see 15–25% fewer "don't recognize this charge" disputes. On a portfolio doing 0.6% dispute rate with 90% "don't recognize" mix, moving to 0.45% saves a dispute-fee-heavy line. For a $2M volume brand, that's roughly $3K/yr saved, zero integration cost, one support seat.
Why multi-brand operators care
The city/state field is set per-transaction on most processors — so you can put a distinct support number per brand while sharing one MID. Combined with a dynamic primary descriptor per brand, every customer statement reads like they bought from a real standalone company, not a shell.