I just got this letter also for my 2024 return. The IRS adjusted my return because the taxable portion of my Social Security disability (SSDI) benefits wasn’t calculated correctly. (I don't even receive social Security but that's a whole other issue!)
After looking into it, we realized the issue was tied to the IRS rule that says up to 85% of Social Security benefits can be taxable, depending on your total income and filing status. In my case, my income was high enough that more of my SSDI should have been taxed. The IRS recalculated it using the method outlined in Publication 915, and their numbers actually make sense.
It appears that TurboTax didn’t apply this rule correctly in my return, which led to the discrepancy. That said, this issue likely only affects a specific subset of users — mainly those receiving SSDI and having enough other income to trigger the 85% rule. So while it’s a real issue, it wouldn’t affect millions of people as the OP claimed.
