Unfiled tax returns create an escalating series of IRS enforcement actions — from Substitute for Return (SFR) assessments that inflate your tax liability, to penalties exceeding 25% of the tax owed, to potential referral for serious investigation. For high-income taxpayers with complex returns involving K-1 partnerships, multi-state income, and international holdings, falling behind on filing is more common than most realize. The IRS Fresh Start initiative and its voluntary compliance policies offer pathways back into good standing, but the window to act narrows once the IRS initiates enforcement. Neil Jesani Tax Resolution has helped clients resolve six or more years of unfiled returns, reducing liabilities by hundreds of thousands of dollars through strategic filing, penalty abatement, and negotiated settlements. What Happens If You Don't File Tax Returns? Failing to file tax returns triggers a predictable and increasingly severe chain of IRS actions. Initially, the IRS sends reminder notices — CP59 and CP515 — requesting that you file. If you ignore these notices, the IRS escalates to a CP516 and eventually a CP518, which is often the final request before enforcement action begins. At this stage, the IRS may file a Substitute for Return (SFR) on your behalf, which almost always results in a significantly higher tax liability than a properly prepared return. Beyond the SFR, the IRS can assess Failure to File penalties (up to 25% of the unpaid tax), Failure to Pay penalties, and interest that compounds daily. Under IRC §6651(a)(1), the Failure to File penalty accrues at 5% of the unpaid tax per month, capped at 25%. When both penalties apply simultaneously, the Failure to File penalty is reduced by the Failure to Pay rate under IRC §6651(c)(1), but the combined effect still compounds rapidly. For high-income taxpayers, these penalties can add tens or even hundreds of thousands...