Correct payroll deduction which should not have been deducted

I have Quickbooks Desktop assisted payroll.  I need to correct a deduction for an employee contribution to an HSA account in a payroll I ran earlier this month.  I deducted a pre-tax deduction for an HSA from an employee's paycheck by mistake.  I need to correct my payroll liability and reimburse the employee the amount.  I know the employee with not get the full amount as I need to make sure the reimbursement gets taxed (as it was previously taken out pre-tax).  I found some previous threads which seemed to describe something close to my problem and were somewhat helpful but now I can't seem to find them again.  But I had some additional questions too.   

-When setting up a new payroll item which I plan to call "Reimbursement for Employee HSA deduction", I am not sure how what expense account to have this payroll item affect?   I assume just "Payroll liabilities"?   

-And when setting up the item, I am not sure what to choose under tax tracking type.  Would it be

"compensation" which is one of the options?  Since I definitely need it to be taxed, so as long as all those taxes are checked on the payroll item set up page, then when I use this payroll item when I run a payroll, will it automatically take taxes out?  

-Lastly, I do not need to issue this employee anymore regular paychecks as he is no longer an employee of ours. Can I just run a paycheck with the addition payroll item for the reimbursement chosen or do I need to do something different since he will not have any hours worked?

Thank you in advance.