The IRS requires all travel expenses to be reasonable and ordinary, and specifically precludes lavish and extravagant expenses from reimbursement.  The following expenses are considered as lavish/extravagant and are not allowed:

• Hotel: Resort Hotel (except for Conference), Suite, Room upgrade
• Meals: 200% of GSA rate
• Rental Car: SUVs or vans for less than 3 travelers, sports car, limousine
• Any upgrade other than additional charges for airfare and rental car for three or more travelers, as mentioned in policy.