Share your insights or perspective on the financial matter presented in the input.

Payroll reimbursments
After reading OP Mark's question and the various answers carefully and also looking over some old pay stubs of mine, I am beginning to wonder if he is mis-reading his pay stub or slip of paper attached to the reimbursement check for the item(s) he purchases.  Pay stubs (whether paper documents attached to checks or things received in one's company mailbox or available for downloading from a company web site while the money is deposited electronically into the employee's checking account) vary from company to company, but a reasonably well-designed stub would likely have categories such as Taxable gross income for the pay period: This is the amount from which payroll taxes (Federal and State income tax, Social Security and Medicare tax) are deducted as well as other post-tax deductions such as money going to purchase of US Savings Bonds, contributions to United Way via payroll  deduction, contribution to Roth 401k etc. Employer-paid group life  insurance premiums are taxable income too for any portion of the policy  that exceeds $50K. In some cases, these appear as a lump sum on the last pay stub for the year. Nontaxable gross income for the pay period: This would be sum total of the amounts contributed to nonRoth 401k plans, employee's share of group health-care insurance premiums for employee  and/or employee's family, money deposited into FSA accounts, etc. Net pay: This is the amount of the attached check or money sent via ACH to the employee's bank account. Year-to-date amounts: These just tell the employee what has been earned/paid/withheld to date in the various categories. Now, OP Mark said My company does not tax the reimbursement but they do add it to my running gross earnings total for the year. So, the question is whether the amount of the reimbursement is included in the Year-to-date amount of Taxable Income. If YTD Taxable Income does not include the reimbursement amount,  then the the OP's question and the answers and comments are moot; unless the company has really-messed-up (Pat. Pending) payroll software that does weird things, the amount  on the W2 form will be whatever is shown as YTD Taxable Income  on the last pay stub of the year, and, as @DJClayworth noted cogently, it is what will appear on the W2 form that really matters. In summary, it is good that OP Mark is taking the time to investigate the matter of the reimbursements appearing in Total Gross Income, but if the amounts are not appearing in the YTD Taxable Income, his Payroll Office may just reassure him that they have good software and that what the YTD Taxable Income says on the last pay stub is what will be appearing on his W2 form.  I am fairly confident that this is what will be the resolution of the matter because if the amount of the reimbursement was included in Taxable Income during that pay period and no tax was withheld, then the employer has a problem with  Social Security and Medicare tax underwithholding, and nonpayment of this tax plus the employer's share to the US Treasury in timely fashion. The IRS takes an extremely dim view of such shenanigans and most employers are unlikely to take the risk.