The general rule is that no "double benefits" are allowed. If you received only partial payment or reimbursement from an employer, you may still be able to claim some portion of the American Opportunity Tax Credit or the Lifetime Learning Credit, based on the amounts of qualified tuition and fees which you personally paid. However, the amount reported in Box 1 of Form 1098-T must be reduced by the amount of any tax-free educational assistance.
Amounts received by an employee under a written educational assistance plan are excluded from taxable income, up to $5,250 per year.
For more information, please see IRS Pub. 970 Tax Benefits for Education.