What is CPA?
Cost per acquisition: a flat one-off payment for each qualifying sign-up, regardless of what that user does afterwards.
CPA pays a fixed amount each time a referred person completes whatever the operator defines as a qualifying action. It is the simplest affiliate model and the easiest to forecast.
Why it matters
The whole risk sits in the phrase qualifying action. Registration, identity verification, a first deposit above a threshold, or a minimum trading volume within a set period are all used, and the difference between them is enormous. A generous-looking CPA attached to a demanding qualification can convert at a fraction of the rate you assumed. Get the definition in writing before you promote anything, and treat any qualification you cannot find in the terms as the least favourable reading. CPA also removes your exposure to negative carryover entirely, which is often worth more than a higher revenue share.