KYB
KYB at onboarding
The point where a business first becomes a customer is also the point where a KYB check has the least existing context to work from - and the most riding on getting it right.
What's different about onboarding specifically
A KYB check run later, as part of ongoing monitoring, has a previous result to compare against - it's looking for a change. A check run at onboarding has nothing to compare to: it's establishing the baseline itself, for the first time, usually while the business on the other end is waiting to actually start using the product.
The trade-off: speed vs. completeness
A shallow onboarding check - confirming the entity exists and is active, without resolving ownership past the first named shareholder - is fast but incomplete: it hasn't actually identified beneficial owners, only shareholders of record. A full resolution, walking the ownership chain to natural persons, is the complete answer but takes longer for a deep or multi-jurisdiction structure. Where that trade-off sits should be a deliberate risk-based decision, not an accident of which check happened to run first.
What happens after onboarding
An onboarding-time KYB result is a snapshot. Whether it needs to be re-checked afterward - and how often - is a separate decision, covered by KYB monitoring and, run continuously, perpetual KYB.
Related
See it work on a real company.