Is there a tax regulation or tax-related law that I could assert that would push back on their arguments about timing of tax liability? ========>>I do not think so You can deduct qualifying expenses paid in the tax year for education during in the year, or education that begins during the year, or education that begins during the first three months of the following year..
Just because the paperwork was received mid January, that was for the previous year. Could my W-2 be adjusted for 2016??============>> no;You usually can claim unreimbursed edu exp on your tax return whe you paid it. "If you receive educational assistance benefits from your employer under an educational assistance program, you can exclude up to $5,250 of those benefits each year. This means your employer should not include those benefits with your wages, tips, and other compensation shown in box 1 of your Form W-2. This also means that you do not have to include the benefits on your income tax return. "