We literally this month had an auditor of one of our plans raise this issue and "demand" it be corrected (and the box on the 5500 checked) before issuing their opinion. Theoretically, I agree - late is late, but 1) the rule is as soon as practicable (and that is open to debate as to what constitutes practicable) and 2) the rule requires segregation from corporate assets - as Peter says, and not "investment" - so the temporary account seems to be the best approach (although, IMHO, that is really rather stupid - as the change in recordkeeper or other reason for the blackout is pursuant to a "fiduciary" decision where their are benefits that should outweigh a slight delay - in other words, "practicable" is, and should be a FIDUCIARY decision....)