In short, whether a transaction will go online, stay offline or be denied, depends on the settings on the card (configured by the issuer) and the settings on the pinpad (configured by the acquirer). The two of them together decide what happens.
So in some cases the combined settings on the card may allow offline processing, which is the batch process in my previous comment. Others, like ATMs (according to the article) will always go online, and yet others may set a "floor limit" - a transaction amount above which the transaction should always go online.
Another factor is the "terminal capabilities", so basically connection speed- if that's too slow transactions may default to offline only.
So what I remember must be that if the transaction is under a certain floor limit, or terminal speed, it can stay offline, maximising some speed-vs-risk tradeoff. And what you note, that the card will deny your transaction when you don't have enough money in the bank, is basically the flip side of that.
What would be harder to notice is the cases when a transaction goes through even when you don't have enough money in the bank, e.g. because the amount you spent is below the floor limit for your issuer and acquirer. But I'm not sure what happens after that- is the transaction declined later? Does the bank charge your account as if it's overdrawn?
It's been a while and I don't remember those things very well I'm afraid :0
In short, whether a transaction will go online, stay offline or be denied, depends on the settings on the card (configured by the issuer) and the settings on the pinpad (configured by the acquirer). The two of them together decide what happens.
So in some cases the combined settings on the card may allow offline processing, which is the batch process in my previous comment. Others, like ATMs (according to the article) will always go online, and yet others may set a "floor limit" - a transaction amount above which the transaction should always go online.
Another factor is the "terminal capabilities", so basically connection speed- if that's too slow transactions may default to offline only.
So what I remember must be that if the transaction is under a certain floor limit, or terminal speed, it can stay offline, maximising some speed-vs-risk tradeoff. And what you note, that the card will deny your transaction when you don't have enough money in the bank, is basically the flip side of that.
What would be harder to notice is the cases when a transaction goes through even when you don't have enough money in the bank, e.g. because the amount you spent is below the floor limit for your issuer and acquirer. But I'm not sure what happens after that- is the transaction declined later? Does the bank charge your account as if it's overdrawn?
It's been a while and I don't remember those things very well I'm afraid :0