ER overpays portion for H&W premiums, can it recover from EE in new plan year?

If a company realizes that it overpaid its portion of H&W premium per pay period for all of 2017 which resulted in an employee 1) not to have their portion deducted pre-tax (since ER credit was enough) and 2) to have additional taxable income can the ER create a payment plan to recover the overpayment in 2018 (per pay period)? ACA considerations (e.g., affordability of coverage in 2018 because paying for benefits of 2017 in new year)? Any thoughts are appreciated. Thanks.

Yes, but you should check with the state laws when this is occurring.  There is no single solution for this, some states are very restrictive while others are not.  

Why would the employee have additional taxable income if the premiums went to pay the health insurance?  Is the plan self-funded and the employee highly compensated?  Also, does the plan document address this?  It may not, but the SPD should address it.  There are lots of issues here.

The employee has additional income BECAUSE his share of the premium was NOT taken out of his paycheck!  Now, there are all kinds of legal issues here. Best is to get an agreement with the employee to have some sort of arrangement over the new year to recover the excess payment, but if the employee does not voluntarily agree, there may be substantial legal barriers to the employer trying to recover the money without the state law of impermissible garnishments applying.  This is a question for a labor lawyer who knows the particular state laws.