Debit card stores transaction details


I read elsewhere that some debit/credit cards store transactions details on them. So I got out my phone and downloaded some free card reader software, and I discovered that two of my cards did in fact store transaction details that could be read contactlessly. One was my TransferWise card, and the other was my Starling Bank card.

The details revealed are just date/time and amount (not the retailer), but they could be read by contactlessly or by a card terminal and so I wondered if there is some reason for storing the details on the card?

I have mentioned this a couple of times in another forum, but nobody came forward with a reason why it might be decided to store transaction details on the card. I haven’t been able to find any information about this online either (maybe I’ve looked in the wrong place) and Starling Bank haven’t got back to me on this yet when I asked them.


I remember reading somewhere that it could be a legacy feature from before internet banking was a big thing?

Essentially by using a card reader with the feature, (like the ones NatWest give out, they don’t have this feature though) you can check the last few amounts taken from your card.

I could be completely wrong, I just remember reading it in a thread ages ago. I think the answer is that it’s legacy rust and activated by default on certain cards by a manufacturer?


Actually, I remember now that someone did mention that to me so maybe it really is just that simple.

I don’t really see it as a problem (though maybe there is a small privacy issue), but I was thinking that maybe it could be used for some sort of interesting security process. It may well be as you say and simply a legacy feature that is just a default setting :slight_smile:

No doubt someone at Starling Bank knows about these things, but they haven’t been able to provide an answer yet.


I wish I’d bookmarked it, as it was an interesting post and now I can’t find it. :frowning:


Initially I wondered if it was anything to do with Oyster and the like to see if it’s been validated or not, you know when they scan it? But I guess it can’t be that if not all cards do it?

I guess Oyster just use the card number instead.


I’ve been told that before; technically the inspector/officer doesn’t know the status of any touch in or out for debit or credit cards. Although, when I asked this it was a few years ago.

I’ve been told they later offload the data and reconcile it against the days touch in and out data.

Theoretically I’ve been told that a bus driver can print a list of the last four digits of the cards used for a journey too?

With Oyster cards, the cards themselves hold the ledger of transactions. I’ve found it can take a good few hours for the TfL website or app to update after a topup, whilst a scan of the card to a reader lists the correct amount.


On that free reader you downloaded… High chance it’s there to skim your card. So be careful on that front.


You’re right. When your contactless card is read by a Revenue Inspector, they’re unable to tell then if it has been used to touch in for the current journey. The card details are crosschecked with the day’s gate data early the next morning and if your contactless card hasn’t been used to touch in, it’ll be charged a penalty fare.