add non-cash income to flex credit

We have a full flex plan working that adds taxable income for our LTD benefit to an employee's check.  (We offer this feature on our plan)  We cannot however, tie a non-cash income code to the full flex plan.  Any ideas on how to tax the benefit but not allow the employee to see the difference between the taxed premium and their taxes paid - essentially no change to their net pay, just an addition to income to be taxed.