Deposit limits
The single most effective tool a licensed casino gives you, and the one most people set too late.
Every UKGC-licensed operator must let you set daily, weekly and monthly deposit limits from inside your account settings, without needing to contact support or give a reason, and must apply a reduction to any of those limits immediately once you confirm it. There is no minimum limit you are required to justify — setting a modest limit on day one, before you have deposited anything at all, is a normal and sensible use of the tool.
Increases work differently, and deliberately so. An operator must not apply a higher limit straight away: a cooling-off period applies, typically 24 hours, and you must actively reconfirm the increase once that period has passed before it takes effect. If a site lets you raise your limit and start depositing more on a single click with no delay at all, that is a licensing condition being ignored and is worth reporting to the operator's named alternative dispute resolution provider or to the Gambling Commission directly.
A sensible limit is one set with a clear head, not adjusted mid-session. A useful way to choose the figure is to ask what you would be relaxed about losing in full, in a month where nothing at all goes your way — not what you hope to win back, and not what a previous big win might suggest you can afford. If you find yourself wanting to raise the limit shortly after setting it, that pattern is itself worth paying attention to, since the cooling-off period exists precisely to interrupt that impulse.
Deposit limits sit alongside other tools rather than replacing them. A loss limit caps what you can lose rather than what you can deposit, a time-out blocks access to the account for a period you choose, and self-exclusion through GAMSTOP blocks every UK-licensed operator at once. A bank-level gambling transaction block, set up directly with your bank rather than with any casino, is independent of all of them and stays in place even if you open an account with an operator you have never used before.