The plan termination date is one thing, the final distribution date is another. Your statement about making contributions after the short year doesn't make sense - let's assume a calendar year plan, term'd on 3/31. Terminated just means no new contributions are accepted (accrued contributions, such as the SH for the prior year, are fine. That plan can stay open for "a while" (generally not longer than 12 months, although going beyond simply means you have to keep the document updated). Let's say you leave it open until Aug 31 in order to complete the contribution, and wait out the 60 day requirement for the other plan (as noted there are workarounds for that but I digress). The deposit is made Aug 15, everyone rolls out on Aug 31. Your short year is 1/1-8/31. No need for any special justification; things just take time.