Some interesting comments about having your credit card can get flagged if you make a small purchase at a convenience outlet and then go on to make a big purchase several hours later. From a comment Cliff left:
When I worked at MBNA (now Bank Of America) the fraud department used a lot of different algorithms to detect fishy behavior on cards. The expiration date is, of course, a dead giveaway. But other indications are things like a small purchase at a gas station or convenience store followed immediately by a ...
I haven’t heard of anything like that happening before over here. Do you guys have chip & pin credit cards? While, far from fool proof, I’m sure it has cut down on workload of credit card fraud departments.