KYC Know Your Customer
KYC is the identity check a regulated financial provider must complete before it can move money for you, usually a government ID plus a photo of your face.
The requirement comes from anti-money-laundering law, not from the provider's preference. A provider that skips it is not being convenient; it is operating outside the rules it is licensed under.
In practice it means uploading a government-issued ID and taking a selfie, once. The check is normally decided within minutes. Some cases are referred for manual review, which takes longer and is not a sign anything is wrong.
Your identity documents are handled by the specialist verification provider that runs the check, under the licence of the regulated partner that operates the payment rail.