Payment terminals requiring update

I was in Kenya last week, and wanted to use my Monzo card for payments. I successfully used it for ATM withdrawal, but had 4 out of 6 card payments fail. After the 4th failure, I gave up.

After the first failure, I contacted customer ops, and (after nearly an hour waiting for a reply) was told that Monzo didn’t even receive the transaction, and it was most likely an issue with an out-of-date payment terminal. The Monzo rep referred it to the acceptance team, but couldn’t do anything more than that.

After each failed payment, I used another card - my Starling, B, amex, and Revolut cards all worked without issue, with the same payment terminal.

My question is, why do payment terminals need to be updated to support Monzo? I thought the whole point of a payment network like MasterCard was that the terminal simply forwarded the details to the network, and MasterCard would take care of querying the issuing bank. If the terminal has to be aware of all new banks, what is the point in MasterCard? And why does Starling work when Monzo doesn’t?

I realise that this may be something that Monzo can’t control, but as a customer that doesn’t particularly care if Monzo succeeds or fails, it does dent my confidence in the product. Regardless of whose fault it is, if my Monzo card fails whilst all others succeed, I’m not going to use Monzo in the future.

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There are numerous potential causes, but BIN-based routing based on old BIN tables is a common one.

To get some more insight:

  1. What was the entry method for these transactions? (e.g. contactless, contact, swiped, keyed)
  2. Do you know if they were all the same acquirer?
  3. Did you get the decline slips, and if so, do they contain any potentially useful data?
  4. How did the terminal react after card entry? (i.e. what was the error message?)
  1. They were all chip + pin.
  2. No idea about acquirer. Two were in the same hotel (front desk + bar), the other two were a supermarket and a petrol station.
  3. I got the decline slip for the first one, which I sent to COps. The others I didn’t keep.
  4. The terminal accepted my pin, then gave an error message of DO NOT HONOR.

I guess this is my confusion. Surely the BIN-based routing should be handled by MasterCard? If the terminal has to be aware of all BINs, why even bother with a card network? It also seems surprising that all terminals I’ve used are fine with Starling BIN, but these all failed with Monzo. What is so different with Monzo? The probability of me hitting several payment terminals with BIN tables that were updated before Monzo but after Starling debit cards were issued seems vanishingly low…

“Do not honor” is often used when a card is cancelled for fraud - since Monzo is positive they didn’t receive the transaction it couldn’t have been them, so presumably the crappy acquirer bank the merchant used has banned Monzo (or whoever had that BIN range before) and is rejecting the transactions on their end.


‘DO NOT HONOR’ - that sounds more like some kind of whitelist or blacklist system that’s likely BIN based. @RichardR might have some insight, and be a good one to report these merchants to.

Agreed, this one seems really odd, and thus I’m not going to speculate as my speculation, unlike on simpler cases, is likely to be way off. Definitely something to make Richard and the Monzo techies aware of.


“Do not honor” is a generic error message that comes up when the withdrawal/payment has been declined for an unknown reason. Normally you have to contact your bank to get this resolved.


Based on a google search, it could be a support for international transactions doesn’t exist.

If it was lack of support for international payments, then surely all UK debit cards would have failed? But my other UK debit cards worked fine less than 30 seconds later…


Yeah, totally get that you managed to make payments using a differnet card/bank. it could possibly be that be that Monzo doesnt support international payments or that loaction based security was inactive or not working correctly

Monzo definitely supports international payments! Given Monzo never got the authorisation request, this isn’t an issue on Monzo’s end.

It’s something weird with the acquirer (since the message never gets to Monzo), but out of my depth so I won’t speculate further!