I am seeking advice about this question:

In a self-insured health plan,
when must deductions from an employee's wages be required to be held in a seperate trust type account?

Here is a very general rule of thumb: Pre-tax contributions do not have to held in trust but after-tax contributions are supposed to be held in trust (unless associated with a cafeteria plan). You’ll want to look at ERISA Technical Release 92-01.