The payments primer
From outside, payments looks like one thing: a customer taps a card and money shows up. From inside it is a dozen loosely coupled systems with different clocks. This primer is the shared vocabulary, so that when someone says "the auth was approved but we never captured," everyone in the room means the same thing.
How it is organised
Three cuts, because most confusion comes from mixing them up.
| Cut | Question it answers | Where |
|---|---|---|
| Roles | Who are the parties, and what does each one do? | Roles |
| Flows | What happens, in what order, on what timescale? | Flows |
| Rails | Which network carries it, and what rules come with it? | Rails |
A single event touches all three. A card payment (rail) runs an authorization (flow) between an issuer and an acquirer (roles).
The idea to take away first
The message and the money are different things, moving at different speeds.
An authorization is a conversation: will you stand behind this? Nothing moves. Settlement is the money, landing hours or days later, in a batch, net of everything else that happened. Almost every "where is our money" question is really a question about the gap between those two.
Two kinds of writing here
Explanations are written as prose, because understanding why something works is not a checklist.
Procedures and scheme rules are written in a flatter, more literal style and set apart like this:
Do one thing per sentence.
- Read the rule.
- Follow the steps in order.
If it looks like an instruction, it is meant to be followed exactly. If it looks like prose, it is meant to be understood.
Numbers and sources
Scheme deadlines are linked to the network's own published documents. Anything that depends on your provider's contract rather than on network rules is labelled as such, because those figures differ per merchant and go stale.
When you meet a term you do not know
The pages introduce terms in the order you need them, and each ends with the ones it introduced. If you arrive in the middle, or a term turns up in a meeting before you have read the page that owns it, the glossary collects all of them with a link to the page that teaches each one.
Test yourself
Reading about payments produces a comfortable sense of understanding that does not survive contact with a real incident. Use the quiz.