If you are required to give back any excess reimbursement, provide your employer with a detailed expense report and meet other requirements. There is no need to report the reimbursement or to deduct the expenses on your return.
Deduction limits are obligatory for your boss, not you, and the floor of 2% of AGI on miscellaneous itemized deductions will not have an effect on your travel and meal costs.
If you are not required to give back any excess reimbursement, the expense arrangement is not an accountable plan and your employer will have already included the reimbursement in your Form W-2. There is no additional reporting requirement.
If your employer reimbursement is less than your actual costs and you wish to deduct your excess expenses, you will need to report the employer reimbursement on Form 2106 as an offset to your expenses.
Caution: Please note that for 2018-2025, only Armed Forces reservists, qualified performing artists, fee-basis state or local government officials, and employees with impairment-related work expenses may deduct their unreimbursed employee business expenses, including travel and meal expenses.