Quick Answer
Yes, but there's a specific line a casino can't cross. A licensed operator can charge a periodic fee on an account that's gone quiet long enough to count as dormant, under rules set by the UK Gambling Commission. What it can't do is wipe out your bonus winnings outright just because you stopped logging in. If a casino's terms claim the right to do that, those terms don't comply with the rules the operator is licensed under.
What "Dormant" Actually Means
Under UK Gambling Commission rules, an account only counts as dormant after 12 months without activity. Before that point, no fee applies and the balance sits exactly as you left it. This catches people out, because casinos often use the word "inactive" loosely in support emails or marketing well before the 12-month mark arrives. The 12-month threshold is the one that matters for fees, not whatever shorter window a support agent happens to mention.
What a Casino Is Allowed to Charge
Once an account passes 12 months of inactivity, the operator can apply what the regulator calls a reasonable periodic maintenance charge. Before it does, it should try to repay your balance to the card, bank account, or e-wallet you last used. It has to explain the fee in its terms and conditions. And it must warn you at least 30 days before the fee starts, naming the date it'll apply. The fee itself has to be proportionate - the regulator doesn't set a fixed figure, but it's explicit that disproportionate or unreasonable charges aren't allowed.
What a Casino Isn't Allowed to Do
This matters because it's the opposite of what the phrase "inactivity fee" suggests on its own. The regulator has named and banned specific terms it has seen operators use in practice - removing winnings or voiding an account after a short window such as 90 days without login, forfeiting a balance after only a 14-day notice period, or stripping a balance of its fund protection after 180 days without login.
A casino can chip away at a dormant balance with a disclosed, proportionate fee. It can't confiscate the whole thing, change what the money legally is, or act as if your right to claim it disappeared because you went quiet. A casino's terms that read like any of the examples above have already been flagged by the regulator as prohibited.
There's one extra wrinkle worth knowing: a periodic charge is specifically permitted where a player hasn't been able to verify their identity within that 12-month window. If a casino can't repay your balance to your card or bank account because the identity checks on the withdrawal were never finished, that's one of the situations the maintenance fee exists for. It also means an operator can hide a dormant balance from your account view entirely, rather than charge against it, provided it has already told you about the balance, your continued right to it, and how to claim it, at least 30 days beforehand.
Why This Applies to Bonus Winnings Specifically
Once a bonus is cleared and the winnings land in your withdrawable balance, the money is yours in every sense that matters under these rules. The regulator doesn't treat money that started as a bonus any differently from a deposit, once it's been through wagering and converted to real funds. The fee rules above apply to the account balance as a whole, not to where any part of it came from.
Operators have a real financial reason for wanting this rule in place. A segregated customer account that nobody logs into still has to be tracked, reconciled, and reported on indefinitely if there's no mechanism for closing it out. The maintenance fee gives them a lawful route to wind an abandoned balance down to zero over time, instead of either leaving it open forever or doing what some operators tried before this guidance existed: writing a term that let them just take it.
How to Avoid Losing Money to This
The fee is easy to avoid: log into the account once in a while, or withdraw a cleared balance rather than leaving it sitting. If you've already stopped using a casino and there's money sitting in the account, check that casino's own terms for its inactivity window and fee amount - these vary by operator. The 12-month threshold and 30-day warning above are the minimum the regulator requires, not a figure every casino uses. Some operators apply the fee as soon as that 12-month mark passes; others wait longer.
The clause itself is usually easy to find once you know what to search for. Open the casino's terms and conditions and search the page for "dormant," "inactive," or "maintenance fee" - it's almost always grouped under a general account-terms section rather than inside the bonus terms, since it applies to the whole account balance, not just winnings from a specific offer.
A casino that wants your trust publishes its inactivity terms in plain language, not scattered across clauses that each tell half the story. One that doesn't is telling you something before you've ever gone quiet.