The first $5,250 of tuition reimbursement is allowed to be reimbursed to you tax free, and thus wouldn't be included in Box 1 of your W-2. If your reimbursement exceeded that amount, it would be taxable, and included in your wages. The amount above $5,250 is allowed to be used when figuring your education credits.
See: Educational assistance programs can be used to help pay
