@babblefiesta
The additional $250 per month that your employer is paying you is just additional pay, the same as if he gave you a $250/month raise. It doesn't matter what he calls it or why he says he is giving it to you. All payments from your employer are treated as wages. The payments should be included in the payroll and in the wages on your W-2. If your employer is not doing that, he's doing it wrong.
As xmasbaby0 said, if the payments are included in your W-2, as they should be, you do not have to do anything special. Just enter your W-2 when you prepare your tax return. If the payments are not included in your W-2, whether or not you get a 1099 for them, post back here when you are ready to prepare your 2022 tax return and we will tell you how to report the income in TurboTax, in spite of the incorrect handling by the employer.
The monthly payments are not expense reimbursements because you are not reporting your actual business expenses. You are receiving the payments under what the IRS calls a "nonaccountable plan," because you do not account for your actual expenses. There is a discussion of accountable plans and nonaccountable plans on pages 4 and 5 of the IRS publication that TomD8 referenced above. Note the following statement in the description of a nonaccountable plan on page 5.
"Payments, including advances, reimbursements, allowances and so on, made under a nonaccountable plan are taxable wages subject to all withholding when paid or constructively received by an employee."
What the IRS publication says later about specific types of expenses is irrelevant, because the payments are being made under a nonaccountable plan.
Since you are a W-2 employee, under current tax law you cannot claim a tax deduction for any job-related business expenses of any kind. This provision of the law remains in effect at least through 2025.
