503. Upkeep Step

503.1. The upkeep step has no turn-based actions. Once it begins, the active player gets priority. (See rule 117, “Timing and Priority.”)

• 503.1a Any abilities that triggered during the untap step and any abilities that triggered at the beginning of the upkeep are put onto the stack before the active player gets priority; the order in which they triggered doesn’t matter. (See rule 603, “Handling Triggered Abilities.”)

503.2. If a spell states that it may be cast only “after [a player’s] upkeep step,” and the turn has multiple upkeep steps, that spell may be cast any time after the first upkeep step ends.