2026 because the items weren't sent until that year. If $250-$500, the Charity should have sent a written acknowledgment. more stringent rules if over $500 and even different rules if $5000 or more.
12/31 is the worst date to do tax mitigation when a third-party is involved. Often something goes wrong. Usually, this happens when taxpayers try to take RMDs (sometimes even a few days earlier). The funds aren't transferred out until the next year, which means the taxpayer failed to take the RMD for that year. However, at least for RMDs, corrective action can be taken.
