Does trample damage carry over if the blocking creature has indestructible?

Trample works by requiring the attacking player to assign lethal damage to each blocking creature before assigning any damage to the defending player (CR 702.19b). Normally, lethal damage equals a creature's toughness minus any damage already marked on it (CR 702.19c).

Indestructible means a permanent cannot be destroyed by damage or by effects that say 'destroy' (CR 702.12b). However, indestructible does not change the amount of damage considered lethal for trample purposes. CR 702.19c explicitly states that when a blocker has indestructible, the minimum damage the attacker must assign to it is still the full amount needed to reduce it to 0 toughness — that is, damage equal to its remaining toughness. Any damage beyond that minimum can be assigned to the defending player.

So indestructible does not give the blocker any extra 'cushion' against trample — it still only soaks up damage equal to its toughness before trample excess flows through.

Concrete example: You attack with a 10/10 trample creature. Your opponent blocks with a 3/3 that has indestructible. You must assign at least 3 damage to the blocker (its toughness), and the remaining 7 damage tramples through to your opponent. The 3/3 survives because it's indestructible, but your opponent still takes 7 damage.

Citations: CR 702.19b and 702.19c govern trample damage assignment; CR 702.12b defines indestructible.