The whole issue of casinos changing their payout percentages is a contentious one. However, the general answer should be no. Here is why: While there is no statutory minimum RTP percentage in the UK for online slots, as such, software providers are at liberty to set their payout levels. Though they have this freedom, RTP is tested over millions of spins and games are certified to ensure they payout the advertised RTP. What’s more, licensed UK online casinos are subjected to regular tests by independent testing boards. The boards themselves undergo a thorough licensing process. They are mandated to test all games in the online casino, ensuring they deliver the same RTP percentage as they have displayed and ensure no bias in generating random combinations. You can be 100% assured of consistent and fair RTP percentages if you choose to play in registered and legitimate online gaming boards with renowned testing boards, including eCOGRA in the UK, Gaming Laboratories International in the USA, and Itech Labs in Australia.