In my working life I've designed and built credit card systems over many years. There are two issues - creditworthiness and lost/stolen/fraudulent activity. Each returns a different code to the merchant. If you are refused for credit reasons, there are only two (realistic) scenarios 1. You have overspent (or not paid!). 2. Currency fluctuations mean that the amount 'authorized' didn't match the amount charged when the draft came through (e.g. a charge for 100# is authorized for $150, but when it comes through it's actually charged for $160 - the 'computer' still thinks the $150 charge is coming later). The latter usually 'corrects' itself after around 5 business days, but until then, both amounts are counted against your limit. To protect against this, get your limit raised before you go!

The fraudulent issue is both technically difficult and not well understood (usually) by customer service agents. Most aren't extensively trained in neural nets and so-called 'intelligent' systems (nor are they paid to be experts). I've been the victim myself of 'false positives' (the system thinks genuine purchases are fraudulent) and a counterfeited card. Usually, talking to a person (use the toll-free number on the back of your card; if the office is closed e.g. because of time differences, escape into the stolen/lost card option on the menu; that's usually staffed 24 hours) telling them who you are, where you're calling from, when you started travelling and other purchases made this week (or day) will satisfy them - they have a screen that shows all attempted authorizations. However, if your card has been compromised then it will (and should be) cancelled (which may leave you temporarily cardless), but for all 'reasonable' purchases (e.g meals but not buying a $5000 camera) the purchase would probably be OK'd - people who steal cards generally don't sit around in a restaurant for several hours risking arrest, they buy relatively 'liquid' assets (such as electronics). Of course, each issuer has different policies, but if they're not 'reasonable' and you are polite, then please feel free to give them my name - they certainly neeed some consulting expertise!!!!!!!

Telling the company you're travelling is not a 'bad' idea, but it won't prevent the initial problem. The computer can't read those notes put on your account (and the decline is nearly always in the authorization system, which probably doesn't even access the notes), so you have to get to a person anyway.

And my experience is that I've had more declines from 'communications' problems than from the computer system. The request needs to get from the point of purchase to the restaurant/store's bank computer, to a 'national' link, to an 'international' link and then back through the local links to the issuer's computer. Any of these can have a glitch - but you only care when it happens to you. (I've been able to tell this by checking on the codes in my bank's computer - which weren't there as the request never made it through). And if a link is broken it may take hours to fix. The `end-to-end' target time for this is about 3 seconds total. The systems I designed had less than a second to make the `decision'. Absolutely no time to transfer to a real person who will read notes on an account.

>From a technical point of view, the issue is not 'informing that you're travelling' - it's deleting that information when you return. I recall checking my own account to discover the note: Do not call customer for liquor purchases. He buys a lot. I'm not sure how that affected my credit rating, but it came (I think) because one of my wine suppliers (who sends a catalogue) used to process the credit card orders after midnight, so the fraud system 'thought' I was regularly buying large amounts of liquor at 3am. And it tripped the fraud model every time

Alan Gardner