Does combat damage use the stack in Magic: The Gathering?

Since the rules update that accompanied Magic 2010 (July 2009), combat damage no longer uses the stack. Under CR 509.5, once blockers are declared and damage assignment is complete, combat damage is dealt all at once — no player receives priority to cast instants or activate abilities in between damage being assigned and damage being dealt.

This means you cannot, for example, use a damage-assignment step trick to kill a blocker with one spell and then have your attacker deal damage to the player as if unblocked. A blocked creature remains blocked (CR 509.1h), and all damage resolves in the same moment.

After combat damage is dealt, the game does check state-based actions (CR 704) and then players receive priority again, so triggered abilities that trigger from combat damage (like lifelink or deathtouch triggers, though note lifelink is a replacement effect) do go on the stack at that point.

Concrete example: Your 2/2 is blocked by your opponent's 2/2. You have a Lightning Bolt in hand. You cannot deal combat damage first, wait for the stack, then bolt the blocker to save your creature. Both 2/2s deal damage simultaneously, and both die to state-based actions after damage is dealt.

Relevant rules: CR 509.5 (combat damage step), CR 509.5a (damage dealt simultaneously), CR 704.3 (state-based actions checked after damage).