Magic: The Gathering Turn Structure
by April King (marumari). Last updated 01/24/2015. Printable PDF version.

The table below shows the structure of a single turn from start to finish. The first column contains the five phases of the game, the second column has the steps that are in each phase, and the third column lists the actions that must be taken during that step, in order.

Phase Step Actions
Beginning Phase
Untap
Phasing happens. All phased out cards phase in and all cards with phasing which are in play phase out simultaneously.
Active player untaps all permanents they control.
Unused mana empties from each player's mana pool.
Upkeep Abilities triggered during the untap step and "at beginning of upkeep" triggered abilities trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
Draw Active player draws a card. This is a turn-based action that does not use the stack.
Abilities triggered "at the beginning of the draw step" and from the active player drawing a card trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
Precombat
Main Phase
  "At beginning of next main phase" and "at the beginning of precombat main phase" triggered abilities trigger. A
When the stack is empty, the active player gets priority to cast spells and play lands. B
Unused mana empties from each player's mana pool.
Combat Phase
Beginning of
Combat
"At beginning of combat" triggered abilities trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
Declare
Attackers
The active player declares his attackers. If no attackers are declared, the Declare Blockers and Combat Damage steps are skipped.
Triggered abilities that trigger off attackers being declared trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
Declare
Blockers
The defending player declares his blockers and which attacking creatures they will block.
For each attacking creature that has become blocked, the active player declares the order that combat damage will be assigned to blockers.
For each blocking creature, the defending player declares the order that combat damage will be assigned to attackers.
Triggered abilities that trigger off blockers being declared trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
If a spell or ability causes a creature on the battlefield to block an attacking creature, players declare that creature's relative placement in the order that combat damage will be assigned to and by that creature's blockers.
If a creature is put onto the battlefield blocking, the active player declares its relative placement in the order that combat damage will be assigned for that creature's blockers.
Unused mana empties from each player's mana pool.
Combat
Damage
First & Double Strike
Combat Damage
If no attacking or blocking creatures have first or double strike, then skip this substep.
All attacking creatures with first or double strike assign combat damage to their blockers.
All unblocked creatures with first or double strike assign combat damage to defending player or declared planeswalkers.
All defending creatures with first or double strike assign combat damage to their attackers.
All assigned damage is dealt simultaneously. This does not use the stack, and may not be responded to.
"Deals combat damage" and "is dealt combat damage" triggered abilities trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
Combat Damage All attacking creatures without first strike assign combat damage to their blockers.
All unblocked creatures without first strike assign combat damage to defending player or declared planeswalkers.
All defending creatures without first strike assign combat damage to their attackers.
All assigned damage is dealt simultaneously. This does not use the stack, and may not be responded to.
"Deals combat damage" and "is dealt combat damage" triggered abilities trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
End of
Combat
"At end of combat" effects trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
All creatures and planeswalkers are removed from combat.
"Until end of combat" effects end.
Unused mana empties from each player's mana pool.
Postcombat
Main Phase
  "At beginning of next main phase" and "at the beginning of postcombat main phase" triggered abilities trigger. A
When the stack is empty, the active player gets priority to cast spells and play lands.
Unused mana empties from each player's mana pool.
Ending Phase
End
"At the beginning of the end step" or "At the beginning of the next end step" triggered abilities trigger. A
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
Cleanup The active player discards down to his maximum hand size (usually seven).
Simultaneously remove all damage from permanents and end all "until end of turn" or "this turn" effects.
Check for state-based actions and triggered abilities, such as those that trigger "at the beginning of the next cleanup step". A
If no state-based actions or triggered abilities occur, unused mana empties from each player's mana pool and the cleanup step ends.
The active player gets priority to cast instants, spells with flash, and to use activated abilities. B
Unused mana empties from each player's mana pool.
Repeat the cleanup step.
Legend for all noted steps:
A Active player orders and adds their triggered abilities to the stack first, then the nonactive player orders and adds their triggered abilities to the stack.
B Game checks for state-based actions first, whenever a player receives priority. Then, both players must pass priority in succession without the other player casting a spell, activating an ability, or taking a special action, for the turn to continue.