Publication 17
taxmap/pub17/p17-149.htm#en_us_publink1000174052How you treat reimbursements depends on the arrangement you have with your
employer.
There are two basic types of reimbursement arrangements—accountable plans and nonaccountable plans. You can tell the type of plan you are reimbursed under by the way the reimbursement is reported on your Form W-2.
For information on how to treat reimbursements under both accountable and nonaccountable plans, see
Reimbursements in chapter 26.