After an IRS Audit: Avoid Carryover Traps, Reporting Mistakes, and Closed-Year Surprises
An IRS tax audit can change much more than the federal tax year under examination. That is especially true when the audit touches deductions, timing, basis, or expense items that created or affected a net operating loss. For taxable years beginning on or after January 1, 2025, California state generally conforms to the Internal Revenue Code as of January 1, 2025, but California still keeps many important differences from federal law. California individual returns back out the federal NOL and requires the taxpayer to compute the allowable California NOL separately on form FTB 3805V. California individual instructions expressly say the allowable California NOL carryover is different from the allowable federal NOL carryover. Federal law also continues to follow its own NOL framework, including the general rule that post-2020 NOLs are carried forward rather than back, except for certain farming losses, and that many post-2017 federal NOL deductions remain subject to the 80% taxable-income limitation.
That means a taxpayer cannot safely take an IRS Revenue Agent Report, plug the revised federal numbers into California, and assume the answer is right. California’s current forms still require a separate California NOL computation, and California continues to apply its own carryover rules, suspension rules, disaster exceptions, and residency-sourcing rules. After an IRS audit, the correct question is not just whether the federal NOL changed. The real question is how that federal adjustment changes the California NOL, the California year in which it is used, and the California years that may need to be recomputed.
Note: An NOL carryforward can be challenged at any point in the future. That effectively opens the NOL calendar year up for audit to prove out the NOL carryforward in any future tax year that comes under audit.
California’s Current NOL Rules Create Fresh Post-Audit Risk
For taxable years 2024 through 2026, California state suspended the NOL deduction for many taxpayers. Individual taxpayers are not affected by the suspension if their net business income or modified adjusted gross income is less than $1 million. Corporations are not affected if their income subject to California taxation is less than $1 million. Disaster loss carryovers are also exempt. Even during the suspension, taxpayers still compute and carry over the NOL, and the carryover period is extended for years in which the deduction is suspended.
California state also does not use a single NOL rule for every loss year. For most general California NOLs incurred in taxable years beginning on or after January 1, 2008, the carryforward period is 20 years. But California state historically allowed carrybacks for certain NOLs incurred in taxable years beginning on or after January 1, 2013, and before January 1, 2019, with the allowable carryback percentage varying by loss year. For taxable years beginning on or after January 1, 2019, California no longer allows NOL carrybacks. That means a current IRS audit can still affect an older California loss that arose under a different carryback or carryforward regime than today’s law. A taxpayer who assumes every audited loss simply carries forward for 20 years can miscompute the California result.
An IRS Audit Can Change Different California Years Than the Federal Years it Changed
One of the biggest surprises comes from timing. California state audit procedure materials specifically recognize that a federal adjustment can affect California tax in different years for carryover items, such as net operating losses. In other words, the IRS may adjust one federal year, but the California tax effect may land in a different California year because the loss was created, limited, suspended, sourced, or used differently under California state law. That is exactly why NOL cases become more dangerous than ordinary audit adjustments.
California’s own NOL instructions reinforce that point. For individuals, California looks only to California-source income and losses in determining whether a nonresident or part-year resident has a California NOL, and a change of residency requires the NOL carryover to be restated under California’s residency rules. So if an IRS audit changes a federal loss year, California may require a separate recomputation that turns on sourcing and residency, not just the revised federal adjusted gross income. After an IRS audit, the taxpayer should therefore review every California year in which the NOL was generated, absorbed, suspended, or carried forward, not just the federal year named in the audit report.
The Reporting Deadlines After an IRS Audit Are Short, and the Notice Must Be Detailed
If an IRS audit changes your federal tax return, California state expects prompt action. If the federal change means an individual owes additional California tax, the taxpayer must report it within 6 months of the final federal determination. If the federal change supports a California refund, the taxpayer generally must claim it within 2 years of the final federal determination. Corporations must file Form 100X or otherwise report the federal changes within six months after the amended federal return or final federal determination, and partnerships must file an amended California return within six months of the final federal adjustments.
Just as important, California does not want a bare notice that “the IRS changed my return.” The notice must be sufficiently detailed to allow computation of the California tax change. California’s publication on federal tax adjustments explains that the taxpayer should provide the complete final federal determination or audit report, including all schedules, copies of the original and revised schedules and forms, and sufficient information to show the effect on credits and carryovers. That matters enormously in an NOL case because the real California issue often lies in the carryover math, not the face amount of the federal adjustment.
The statute consequences can be harsh. If California state receives sufficiently detailed notice of the federal changes within six months of the final federal determination, it generally has two years from the date it receives that report to apply the federal changes to the California return. If the notice comes after six months, California generally has four years from the date it receives sufficiently detailed information. If neither the taxpayer nor the IRS timely notifies California, the California assessment statute remains open, and the Franchise Tax Board may assess at any time. On the refund side, if the taxpayer does not file the California refund claim within the required period, the overpayment cannot offset other amounts due, and no refund can be issued. Those rules are where many post-audit NOL surprises become expensive.
Contact the Tax Law Offices of David W. Klasing if an IRS Audit Threatens Your California NOL Carryovers
At the Tax Law Offices of David W. Klasing, we handle post-audit NOL issues as multi-year state and federal controversy matters, not as simple amended-return projects. Our boutique California tax firm is comprised of award-winning, nationally recognized Tax Attorneys and CPAs, and we combine over 75 years of tax and business experience to resolve complex federal, California, and international tax issues. That matters because a disputed NOL usually affects more than one year, more than one return, and more than one taxing authority.
Our dual-licensed Tax Attorneys & CPAs at the Tax Law Offices of David W. Klasing can help trace the audited adjustment back to the original California loss year, recompute the California carryover under the correct historical rule, determine whether suspension-year extensions apply, and prepare the federal-change notice with the level of detail California actually requires. Where an IRS audit touches overstated deductions, false expense support, altered books, or other facts that could create fraud exposure, our CPAs work under attorney supervision as part of the legal team to support legal advice and help preserve applicable attorney-client privilege and work-product protections as the law allows.
If an IRS audit just reduced a federal loss, disallowed deductions that generated a California NOL, or left you wondering which California years now need correction, this is the point to act with precision. NOL problems become much harder and much more expensive when taxpayers report the federal change late, miscompute the California carryover, or miss the refund window while trying to sort out the math. At the Tax Law Offices of David W. Klasing, we help clients protect the carryover, protect the statute, and protect the case before a federal adjustment turns into a much larger California tax problem. Call the Tax Law Offices of David W. Klasing at 800-681-1295 for a confidential, reduced-rate initial consultation HERE.
