Why slot RTPs differ at different casinos

Why do some slots have different RTPs at different casinos? The short answer

When a studio builds a slot, it often prepares more than one maths model with different RTP settings. Each version is tested and certified, and casinos then decide which version to put in their lobby. That's why one casino's help screen may show 96.5% for a game while another shows 94.5% for what looks like the same slot.

Nothing about this is hidden or illegal, but it isn't advertised either. Reviews, including ours, usually quote the default or highest figure, so the only reliable number is the one in the help screen at the casino where you're playing. Wizard of Odds notes in its slots guide (opens in a new tab) that a single title's RTP can also differ from one jurisdiction to another. For more answers on slot maths, visit our questions hub.

Slot RTP versions: examples from well-known games

These versions come from the developers' published figures as recorded in our reviews. The highest figure is usually the one quoted in marketing.

Many other entries in our slot reviews carry the note 'lower versions exist'. When you see that, assume the casino could be running any of them until the help screen tells you otherwise.

What a lower RTP version costs you in pounds

The difference looks tiny as a percentage. In money it isn't. Your expected loss is the total you stake multiplied by the house edge, and the house edge is 100% minus the RTP. Here's Slayers Inc, using two example sessions: 400 spins at 50p (£200 staked) and 1,000 spins at 50p (£500 staked).

The lowest version costs more than three times as much as the highest for exactly the same game. On Bigger Bass Bonanza the spread is smaller but still real: £32.90, £43.30 or £53.80 per £1,000 staked depending on whether the casino runs 96.71%, 95.67% or 94.62%. The house edge calculator lets you plug in any figure.

These are long-run averages. A single session can finish well above or below them, but over time the lower version takes more of your money.

Other reasons a slot's RTP can differ

Casino-chosen versions are the main cause, but not the only one. These also change the figure you see:

• Country: the RTP of one title can differ between jurisdictions, so a figure quoted for another market may not match the British version.
• Stake level: some games pay a different RTP at different stakes. Reels of Gold is listed at up to 96%, varying with stake, Rainbow Riches Pick 'n' Mix at about 94% to 96% depending on stake, and Mega Joker reaches up to 99% only at its top stake with the Supermeter.
• Bet modes: optional modes can shift the figure slightly. Sweet Bonanza Xmas is listed at 96.48%, or 96.51% with its Ante Bet.
• Features not offered in Britain: Extra Chilli Megaways is quoted at 96.82% including Feature Drop, a bonus buy, but up to 96.41% without it, which is the version relevant in Great Britain.
• Jackpot contributions: progressive games may quote RTP with or without the jackpot share. Mega Moolah's base game is listed at 88.12% excluding its jackpot contribution, while Divine Fortune's 96.59% includes about 4.07 points of jackpot contribution.

The last point catches people out. On a progressive jackpot slot, part of the RTP only comes back to whoever wins the pot, so most players experience something closer to the base-game figure. Our jackpot slots guide explains this in more detail.

Why a casino might run a lower RTP version

Casinos don't publish their reasons, so we won't guess at any one operator's thinking. The commercial logic is simple, though: on a lower setting the casino keeps more of each pound staked on average, while a higher setting offers players better value. Each operator balances those differently, and may pick different settings for different games.

Costs form part of that picture. Remote gaming duty, paid by operators on their gaming profits, rose from 21% to 40% on 1 April 2026, as covered on our gambling tax page. Gambling winnings aren't taxed for UK players. Whatever the reason, the effect for you is the same: two casinos can charge different prices for the same slot, and the help screen is where that price is shown.

UK rules on showing a slot's RTP

• RTP before you play: under RTS 3 (opens in a new tab), information on your chances, which for games of chance means the average theoretical RTP, must be available before you commit to gamble.
• No changes mid-play: rules, payouts and probabilities can't change while a game is available for play.
• No adaptive maths: online games can't adjust outcomes to hit a target return.
• Tested before release: under the Commission's testing strategy (opens in a new tab), a test house checks game design, software and the actual RTP by simulation, and games can only be released once the report reaches the Commission.
• No minimum RTP: no rule sets a minimum RTP for online slots in Great Britain, which is why low versions can be offered legally.

The Commission publishes a list of approved test houses (opens in a new tab), and our page on RTP information rules covers what a help screen must contain. See also how RTP must be displayed.

Can a casino change a slot's RTP while you're playing?

No. The Commission's standards stop a game's rules, payouts and probabilities changing while it's available for play, and every version must have been tested before release. A casino can't quietly lower the RTP during your session or after a big win. Any switch to a different certified version would show its own RTP in the help screen, which is why checking each time you play a game somewhere new is a good habit. We cover this in more depth in can casinos change a game's RTP?.

How to check which RTP version your casino runs

1. Open the slot, but don't spin yet.
2. Tap the info, help or 'i' button, or the menu icon, and look for 'Return to player' or 'RTP'.
3. Note the figure and compare it with the developer's headline RTP from a review.
4. Check whether the RTP changes with stake, bet mode or jackpot contribution; the help screen should say.
5. If you have accounts at more than one casino, compare the help screens there too.
6. Work out your expected cost with that figure before you set your stake and budget.

Myths about slot RTP at different casinos

Checking slot RTPs at our partner casinos

We can't tell you which RTP version each partner runs for a given game, because versions are set per game and can differ between lobbies, so open the help screen of any slot before you play. The offers below are slot offers; table and live games are often excluded or count for less towards wagering. 18+ and terms apply.

Casumo (Recro Limited, UKGC account 61549) gives new customers who opt in a 50% bonus up to £100 on a minimum first deposit of £20, with 10x wagering on the bonus within 7 days and a £5 maximum bet while it's active. Game, play and payment restrictions apply, so check which slots count.

10bet (Blue Star Planet Limited, account 43173) offers new UK customers a 100% match up to £25: choose the casino welcome bonus at sign-up, deposit within 7 days, then wager the bonus 10x on slots within 3 days. Maximum bonus winnings are £1,000, and Skrill and Neteller deposits are excluded.

Coral (LC International Limited, account 54743) gives new players 100 free spins at 10p each on selected games after they deposit and bet £10 or more on slots between 1 October 2026 and 1 February 2027. Accept the spins within 48 hours and use them within 7 days; winnings carry no wagering. Paying in with Neteller, PayPal, Paysafe, Skrill, a prepaid card or certain debit cards rules you out. The RTP of those spins depends on the version of the selected games Coral runs.

18+. Every casino game has a built-in house edge, so over time you should expect to lose what you stake. Set a budget before you play and stop when it’s gone: safer gambling tools and support. Free, confidential help: National Gambling Helpline 0808 8020 133.