Mastercard Reason Code 4870: Chip Liability Shift

What Mastercard reason code 4870 means

4870 is a fraud code built on the EMV liability shift. Chip cards are much harder to counterfeit than magnetic stripes, so the networks agreed that whoever is less prepared for chip absorbs the cost of counterfeit fraud. If a criminal copies the magstripe of a chip card and uses the clone at a terminal that only read the stripe, the issuer can charge back under 4870 and the merchant’s side carries the loss.

The cardholder’s role is simple: they report the transaction as fraud, and the issuer checks how the card was read. Liability-shift dates and scope have varied by region and by merchant type (for example, automated fuel dispensers moved later than standard point-of-sale in some markets), so confirm the rules that apply to your terminals.

Does 4870 affect ecommerce merchants?

Almost never. Card-not-present transactions don’t involve reading a chip, so there’s nothing for liability to shift on. Online fraud claims come in as 4837 or 4863 instead. A 4870 on an ecommerce merchant account usually means a coding or mapping error worth querying with your acquirer.

Merchants with a physical presence alongside an online store, such as showrooms, pop-ups and trade-show booths, are the ones exposed.

Common causes

• Terminals that are not chip-capable, or chip readers that are switched off
• Fallback transactions, where the chip read fails and staff swipe the stripe instead
• Mobile card readers that only support magstripe
• Staff keying card numbers manually at the counter
• Counterfeit card rings targeting merchants known to swipe

Evidence that wins a 4870 dispute

1. POS entry mode from the authorization showing the chip was read (not swiped or keyed).
2. Chip cryptogram data from the transaction, which your acquirer can provide.
3. Card type: evidence that the card was not a chip card, so no liability shift applies.
4. Terminal certification showing the device is EMV-capable and was operating as such.
5. Fraud-reporting status: issuers are generally required to report the transaction as fraud before charging back.

If the transaction was swiped or keyed on a chip card, there’s usually no defense.

How to prevent 4870 chargebacks

• Use EMV-certified terminals everywhere you take cards in person, including mobile readers.
• Train staff to retry the chip, then decline, rather than swiping as a fallback, or set the terminal to limit fallback.
• Prefer contactless and chip over keyed entry.
• Review fallback rates by location and terminal; a spike is an early warning.

Should you fight or accept?

Fight when your logs show a chip read, or the card had no chip. These cases turn on data, and the data either supports you or doesn’t.

Accept when the stripe was swiped or the number keyed on a chip card. The liability shift is doing what it was designed to do. Upgrade or reconfigure the terminal involved, and compare with 4871 Chip/PIN Liability Shift, which covers lost and stolen cards where PIN wasn’t supported.