Eligible for FSA/HSA (flexible spending account / health savings account) cards in the US — the card checks the MCC, plus an item-level standard called IIAS (Inventory Information Approval System), before approving.
The MCC quietly sets the interchange rate, whether the purchase earns rewards, whether it's treated as a cash advance, and how risk models see the merchant. Acquirers assign it at onboarding — and miscoding is a compliance problem, not a shortcut.
Merchant Category Codes are defined under ISO 18245, with network-specific usage on top. Around 500 exist; the ones that come up in real conversations are in our lookup tool.