Have a client who wants to designate his spouse as the primary beneficiary of his 401(k) account. No problem.

Next, he wants to name his daughter as contingent beneficiary if she is age 18 or over at the time of his death. Otherwise, benefit would go to a trust established for the daughter's benefit.

Anyone have issues with this?

No problem as long as the trust instrument is provided to the plan administrator. Verifying the daughter's age at the time of EE's death is a nice bright line--either she is under age 18 or not on EE's date of death. Should not be a problem to administer.