All licensed bookmakers have to follow a certain set of rules and regulations, including providing the Know Your Customer (KYC) verification. KYC verification is used to battle money laundering and help bookmakers identify users.
So, while it may seem like the bookmakers asking for your documents is a breach of your personal information, they’re required to do so by betting regulators. Worry not, however, as all details you provide to the betting site will remain safe.