Successor plan - when can new plan start?

A plan terminated in 2019 with last distribution say 10/31/19. One year wait is 10/31/20.  I know a new plan could start 1/1/21 for sure. What about anything in 2020? Could they do a short plan year say 11/1/20-12/31/20 and have everything prorated? Safe harbor would be a no go.

Pre 1.401(k)-1(d)(5)(i), the new plan cannot be in existence within the 12-month period after the date of final distribution of assets. So it would seem that in your hypothetical the new plan could come into existence as early as 11/1/2020 without spoiling the prior termination, jmartinrps.

And of course, not everything gets prorated, since the 19,500 is still allowable as the deferral maximum.  (Just might be harder to pass an ADP test if the owner tries to cram it all in with no staff employees doing anything close to that.)