Substantiated employee business expense reimbursements are reported on box 12 of Form W-2. If you don't use this expense, the unused amount would be taxed as wages.
See Entering in Program - Form W-2.
Once you've entered your wages from Form W-2, complete IRS Form 2106 to report employee business expenses. To enter your information for Form 2106 in the TaxAct program:
The total of the expenses you enter will transfer to Line 7 of Form 2106. TaxAct automatically places the amount on Line 7a (reimbursements for expenses other than meals and entertainment).
If you have more expenses for meals and entertainment, move the reimbursement to Line 7b (reimbursements for meals and entertainment) on Form 2106, or make the change on the Employee Expenses – Employer Reimbursements screen. Enter a zero on Line 7a and enter the reimbursement amount on Line 7b.