The per diem is used as "housing allowance" to pay for a secondary residence closer to their office
The following exerts from Appendix Q do not directly address the situation but they do give some guidance in what to maybe look for when using this type income.
9. Employer Differential Payments. If the employer subsidizes a consumer's mortgage payment through direct payments, the amount of the payments:
a. Is considered gross income, and
b. Cannot be used to offset the mortgage payment directly, even if the employer pays the servicing creditor directly.
The following premise that only the amount that exceeds the actual verified expenses are considered income would be applicable IMO.
12. Automobile Allowances and Expense Account Payments.
a. Only the amount by which the consumer's automobile allowance or expense account payments exceed actual expenditures may be considered income.
b. To establish the amount to add to gross income, the consumer must provide the following:
i. IRS Form 2106, Employee Business Expenses, for the previous two years; and
ii. Employer verification that the payments will continue.
c. If the consumer uses the standard per-mile rate in calculating automobile expenses, as opposed to the actual cost method, the portion that the IRS considers depreciation may be added back to income.
d. Expenses that must be treated as recurring debt include:
i. The consumer's monthly car payment; and
ii. Any loss resulting from the calculation of the difference between the actual expenditures and the expense account allowance.
_________________________
The opinions expressed are mine and they are not to be taken as legal advice.