What is the penalty for missing a day of stoning?

Missing a day of stoning (Rami) at the Jamarat does not invalidate your Haji, but it does require compensation. The stoning on the Days of Tashreeq is considered wajib (wajib) menurut jumhur ulama, not a pillar (rukun), so missing it requires fidyah but does not void the ibadah haji.

If you miss the stoning on one day, you can make it up the following day. Perform the missed day's stoning first (all three pillars in sequence), then perform the current day's stoning. The stoning must be done in chronological order — you cannot stone for day 12 before completing day 11. All makeup stoning must be completed before sunset on the 13th of Dzulhijjah (the last day of Tashreeq). If you departed Mina early on the 12th, the deadline is sunset on the 12th.

If stoning is missed entirely and cannot be made up within the allowed time period, a fidyah (sacrifice of a sheep in Mekkah) is required menurut jumhur ulama. The Hanafi school holds that missing even one day's stoning without excuse requires dam (sacrifice). If the stoning was missed due to a valid excuse (severe illness, disability), then appointing a proxy is the proper course of action rather than paying fidyah after the fact. In all cases, the Haji remains valid.