MCR means Medical Care Reimbursement deduction chosen under a Medical Care Reimbursement plan. It is deducted monthly from your pay check and will be returned to you after you have paid a medical bill. This money is tax-sheltered, it allows you to put aside pre-tax dollars out of your pay for eligible medical expenses. Office visit copayments, prescription copayments, orthodontics, and eyeglasses are eligible for reimbursement.
In order to get reimbursed, you need file a claim. The medical expense must be incurred by you or an eligible dependent and should not be reimbursable by any insurance or other source.