If you cashout from a casino, there is 0 tax, if you hold on to your wallet and make a profit you need to pay a TAX, I have played on crypto casinos for 3-4 years now, and cashout easily more than £100k and never got any bill from HMRC, if is over £10k win you should cashout like £4k £5k at a time to avoid KYC by wallet or do a cashout on 2-3 different wallets