Fundamentally it's all extensions of credit, right? The question is who is taking on credit risk in these transactions and how is everything settled when the power comes back. Presumably, everything is somewhat reversible and there is some dispute resolution process.
Right. IIRC, the acquiring bank would send an authorisation advice to the issuer when it comes back online. An auth advice is like notice that a payment happened, the issuer doesn’t really get a say in rejecting it (as it does for an authorisation). For the most part, anyway.
If that transaction brings the customer into a negative balance, it’d be between the bank and customer to figure that out. Especially if the customer has no overdraft facility and isn’t supposed to be able to go negative, and isn’t able to easily recover the payment, or the customer is considered vulnerable, then the bank will often just swallow the loss.
