Checks at account opening exist because a licence usually requires the casino to confirm age and identity before anyone gambles with real money. Some sites complete them in seconds by matching the name, date of birth and address against public and credit records, and ask for nothing more. Others ask for uploads straight away and keep the account in a restricted state until a reviewer approves them. The registration page usually says which approach the casino uses.
A passport, a national identity card or a driving licence covers identity at almost every casino. The document has to be valid, fully visible with all four corners in the frame, and readable without glare. Some casinos want both sides of a card. A second document, such as a utility bill, a bank statement or an official letter from the last few months, confirms the address. The accepted list sits in the verification section of the terms.