The U.S. Tax Court’s May 4 ruling in Kadau v. Commissioner (T.C. Memo. 2026-37) applied the enhanced 40% accuracy-related penalty under IRC Section 6662(i) to a micro-captive owner whose premiums ran 2.5 to 3.5 times prevailing commercial rates. The decision marks the IRS’s 12th consecutive Tax Court victory over a micro-captive arrangement and the first to pair a premium-pricing disallowance with the elevated economic substance penalty.
Curtis Kadau operated Surface Engineering, a metal alloy coating business, and routed risk through Risk & Asset, a Nevis-based captive electing under IRC Section 831(b). The captive participated in a risk pool that collected roughly $50 million in premiums but paid out only $17,611 in claims, producing a loss ratio of 0.035%. Funds cycled from the operating company back to the owners through loans and life insurance policies. The court characterized this as circular financing rather than genuine risk transfer.
The court found the arrangement failed both prongs of the economic substance doctrine under IRC Section 7701(o). On the objective test, the structure did not meaningfully change the taxpayers’ economic position. On the subjective test, the dominant purpose was tax reduction, not risk management. Because the transaction lacked economic substance, the court applied the 40% penalty under Section 6662(i) rather than the standard 20% rate.
Who it affects
Self-insured employers and business owners funding retained workers’ comp, GL, or auto liability through 831(b) captives face the most direct exposure. The ruling draws a bright line: premiums that materially exceed commercial rates for equivalent coverage invite not just deduction disallowance but the enhanced penalty. Captive managers, captive board members, and the actuaries preparing feasibility studies should treat the premium-to-commercial-rate comparison as the metric the IRS is now litigating on.
The decision also matters for CFOs carrying a tax contingency reserve against captive premium deductions. A 40% penalty on top of back taxes and interest can push total exposure well beyond a contingency sized to the standard 20% rate.
The reserve mechanism
When the IRS disallows a captive’s premium deductions, the tax benefit that justified the risk transfer collapses. The actuarial cession that moved liabilities off the parent’s balance sheet becomes unsupported, and the ceded reserves effectively unwind back onto the parent. For a self-insured employer, this means the loss reserves that appeared on the captive’s balance sheet revert to the parent’s retained obligation, increasing the carried IBNR on the consolidated statement.
The 40% penalty accelerates the financial exposure. A captive owner who deducted $500,000 in premiums and loses the deduction faces not only the tax on the disallowed amount plus interest but an additional 40% penalty on the underpayment attributable to the transaction. That total can exceed any reasonable tax contingency reserve the parent was carrying.
What this means for your next review
Before your next reserve study or captive board meeting, ask your actuary to benchmark your captive premiums against commercial market rates for equivalent coverage. If the ratio exceeds what an arm’s-length buyer would pay, the Kadau standard says the IRS will treat the excess as a tax shelter, not insurance. Confirm that your captive’s feasibility study includes a documented premium-to-commercial-rate comparison and that your actuarial opinion addresses the loss ratio the IRS is scrutinizing. If you carry a tax contingency reserve for captive deduction risk, resize it for the 40% penalty, not the 20% rate that applied before courts began enforcing the economic substance doctrine against micro-captives.