If the company uses an accountable plan, the reimbursement is not taxable to you and is not reported on your tax return. An accountable plan means that the company only reimburses you for legitimate work expenses that you prove with receipts.
If the company uses a non-accountable plan, meaning that they simply give you an allowance and do not require that you prove you spent the money on legitimate business expenses, then they are required to include the income in your 1099 or W-2 wages, so the money would be taxable but there would be nothing extra for you to report.
