Hitting soft 17 (S17) negatively impacts the player that rule increased the house edge by 0.40%. In some venues, the dealer hits on a soft 17 (abbreviated as S17), though most venues have the dealer stand on soft 17 (S17). Like traditional blackjack, the dealer hits on 16 and stands on 17.All cards have the same values as in blackjack. Spanish 21 is played with 48-card Spanish decks, although standard French suited 52-card decks are used with the 4 ten-spot cards removed. The game is played with six or eight decks dealt from a shoe, or from a continuous shuffling machine (CSM).

Spanish 21 is played on a blackjack table with a custom layout and uses the following rules: In Australia and Malaysia, an unlicensed version of the game, with no dealer hole card and significant rule differences, is played in casinos under the name ' Pontoon'. Unlicensed, but equivalent, versions may be called Spanish blackjack. Spanish 21 is a blackjack variant owned by Masque Publishing Inc., a gaming publishing company based in Colorado.