HCE Definition / Multiple Plans / Different Plan Years

I have a client who sponsors two plans, a calendar year 401(k) plan, and a profit-sharing plan with a November 30 plan year end (the latter is paired with a cash balance plan).

Do I determine highly compensated employees for both plans with respect to the look back year that corresponds to their plan year? It just seems odd to have, perhaps, two different groups of highly compensated employees.

Without doing any research, I believe that it would be separate lookback years for the different plans. Does the PS/DB by chance use the calendar year election? That would at least make it easier to keep track of who is an HCE and who isn't, although it might potentially have other ramifications - ask the cash balance actuary!

No calendar year data elections in any plans.

See regulation 1.416-1, question T-23.  Each plan independently determines the present value of each accrued benefit as of the plan's determination date.  The present values as of the determination dates that fall into the same calendar year are aggregated.  You would then have one combined test for each calendar year.

Fine, but that isn't the question. The question was regarding HCE determination, not Key and Top Heavy.