Casinos that publish payout percentages
Below is a list of casinos that either publish audited retrospective payout percentages or the theoretical RTP figures for their games. Very few casinos publish both these types of information. An explanation of the difference between the two is below. Generally speaking, the fact that a casino allows their payout percentages to be audited and published is one good sign that you are dealing with a reputable organisation.
Our most recent survey and comparison of online and land casino payout rates can be found here: Comparison of casino payout rates for 2013
RTP figures vs audited payout percentages
There are two main ways that casinos can offer an insight into the odds offered by their games: audited retrospective payout percentage reports, or the publication of the theoretical return to player (RTP, aka payout percentage) numbers. In both cases the numbers published are almost always a percentage figure.
Audited payout percentage reports
These reports are published by many casinos, particularly those that are accredited by eCOGRA. The reports consist of a number of percentage figures that reveal the actual payout rates of the games at the casino for the preceding month. For example, if a casino was to report that its slot machines paid out 96.5% over the course of a month, then we know that of all the money wagered on slots during that period, 96.5% of it was returned to players in the form of winnings.
These numbers are, of course, very rarely over 100% as that would imply that the casino has not made a profit. However from time to time it does happen when a player has a significant win. The random and often high variance nature of casino games and slots means that the payout numbers will fluctuate from month to month.
Compared to the publication of theoretical payout rates, these reports give us an insight into the actual performance of the games at a casino and the profitability of said casino. However as the reports commonly group games into broad categories such as slots, table games, and video poker, there is little insight into the payout rates of the individual games themselves. This is where the publication of theoretical return numbers can help, as we explain below.
Theoretical Return to Player (RTP) numbers
A smaller number of casinos, and indeed some software providers such as Net Entertainment and IGT, publish what is known as theoretical RTP numbers for individual games. They are most often found in the game help files, payout tables within the games, or on a dedicated page on the casino's website. These numbers represent the expected long term payout rate of a game based on the rules and mathematics used to construct the game. A RTP number can give you a quick insight into how "loose" or "tight" a slot machine is. At a very high level, the closer the number is to 100%, the "looser" the slot, and the longer your money should last while playing.
However RTP is not the only defining characteristic of a slot machine, as variance has a significant impact on your playing experience too. For example a low variance slot (i.e. with little difference between the top and bottom wins) with a 98% payout rate could quite conceivably be a boring money sucker where you have little chance of getting ahead, while a high variance slot set to 94% could still pay out some gigantic wins from time to time.