Something about what you are saying is "off." First of all, "as of September" makes no sense since this is August 2025. The IRS does not typically send out notices in August to say that you did not file a tax return for the current tax year. What EXACTLY does that notice say? Does it say that you filed a tax return with tax due but that you did not pay the tax? Look closely at your 2024 return. Does it show a refund on line 35a or does it show an amount of tax due on line 37?