Visa Reason Code 10.1

A counterfeit card was used in a chip-capable card-present environment, and liability shifted to the non-chip party.

The transaction was made with a counterfeit card at a terminal that wasn't EMV chip-enabled, or the chip wasn't read, shifting fraud liability onto whichever side didn't support chip.

If your checkout wasn't the point of sale (this almost always only applies to in-person terminals, rarely online), this code usually isn't fightable on standard e-commerce evidence.

EMV chip-read transaction data proving the chip was read at the terminal, if applicable.

Treating this as a standard online fraud dispute when it's actually a card-present, terminal-liability issue.