CAMT guidance delay to 2027 leaves CFOs closing on notices
Treasury's second package of proposed corporate alternative minimum tax rules is not expected until 2027, which means a third year of 15% book minimum tax positions built on interim IRS notices.
The CAMT guidance delay to 2027 turns what was supposed to be a transitional problem into a structural one. Treasury's Office of Tax Legislative Counsel has signaled that the second package of proposed regulations for the corporate alternative minimum tax will not arrive until next year, according to a July 15, 2026 advisory summarizing recent Treasury and IRS remarks. That leaves finance teams computing a 15% tax on book income for a third straight year using interim notices rather than rules, and it pushes the documentation burden squarely onto the CFO's desk this quarter.
What a 2027 timeline actually changes
CAMT itself is not new. The Inflation Reduction Act imposed a 15% minimum tax on adjusted financial statement income for corporations averaging more than $1 billion of AFSI over a three-year period, effective for tax years beginning after Dec. 31, 2022. Foreign-parented multinational groups are pulled in at $1 billion of group-wide AFSI plus roughly $100 million of US AFSI. What is new is the duration of the guidance vacuum. The IRS has issued interim CAMT guidance across 2025 and again in February 2026, each round expanding or refining the adjustments that move book income to AFSI.
Interim notices are usable authority. They are not the same as proposed or final regulations, and they have a habit of being superseded by rules that arrive with retroactive effective dates. A 2027 proposed package means the earliest realistic final regulations land well after the 2026 return is filed. CFOs should plan on the assumption that at least one position taken this year gets rewritten under them later.
The practical consequence is sequencing. Tax and controllership need to decide now which interim positions they are prepared to defend, because the same positions drive Q3 and Q4 estimates, the year-end provision, the return and the disclosure. Deciding at filing is too late.
Why a book-income tax makes the provision move
A liability computed from financial statement income means the tax provision now travels with accounting judgment rather than tax elections. Pension and other post-retirement remeasurements, fair value swings on equity and derivative positions, depreciation conformity mechanics, and purchase accounting from acquisitions all feed AFSI. Each is a place where a reasonable alternative reading of an interim notice produces a materially different number.
That volatility is difficult to forecast and harder to explain. Under ASC 740, a position grounded in a notice rather than a regulation invites a more searching uncertain tax position analysis, and the recognition and measurement conclusions have to be revisited each time the IRS adds an adjustment. Estimated payments compound the problem: underpayment exposure is real, but overfunding a minimum tax on a contested AFSI computation ties up cash for quarters.
Build the reliance memo before the close
The unique control CFOs can put in place this quarter is a reliance memo: a short, standing document that records exactly what the company is relying on, why, and what happens if the authority changes. It is not a technical tax opinion. It is the artifact that lets a CFO sign a provision built on subregulatory guidance and brief the audit committee without improvising.
Four elements belong in it. First, the documentation standard: which notice, which section, which paragraph supports each material AFSI adjustment, and what alternative reading was rejected. Second, the reserve posture: whether the position is more-likely-than-not, what measurement was applied, and the dollar sensitivity if a 2027 rule reverses it retroactively. Third, the disclosure language, drafted once and reused across the 10-Q and 10-K so the description of guidance risk does not drift quarter to quarter. Fourth, the audit committee briefing: a plain statement that the computation rests on interim authority, the range of outcomes, and the trigger events that would require a revision.
Auditors will ask for most of this anyway. Producing it on the company's own timeline, rather than in response to a request during the year-end close, is the difference between a controlled process and a scramble.
New rate reconciliation disclosure removes the cover
The timing collides with expanded corporate tax disclosure. Bloomberg Tax reported in April 2026 that the new disclosure regime is letting investors peer into what had been the black box of rate reconciliation, with far more granularity on the components driving the effective tax rate. CFO.com flagged in February 2026 that shifting tax policy is already reshaping planning assumptions.
The consequence is uncomfortable but straightforward. Investors and analysts can now see CAMT-driven swings in the reconciliation that CFOs cannot yet explain by pointing to settled law. Investor relations, tax and financial reporting should agree on a single narrative for how CAMT affects the rate, what portion is judgment-dependent, and what would change it. Silence reads as a control weakness.
Other items on the near-term guidance calendar
CAMT is not the only open file. Treasury deputy benefits tax counsel Kurt Lawson has indicated guidance on Section 162(m), reflecting the One Big Beautiful Bill Act's expanded aggregation and covered-employee rules for the $1 million pay deduction cap, is expected in the fall. Treasury and IRS officials have also named qualified small business stock, controlled foreign corporation attribution rules, foreign currency gain and loss, meals deductions, sovereign wealth fund effective dates, and paid leave and childcare credits as pending. The 2025-2026 Priority Guidance Plan still lists open corporate items, including final computation regulations for the Section 4501 stock buyback excise tax.
Grant Thornton notes that OBBBA guidance continues to roll out through 2026. Taken together, the pattern is a tax function operating on interim authority across several material items at once. The reliance memo discipline that CAMT demands is worth extending to each of them.
Key takeaways
- Treasury's second CAMT proposed regulation package is not expected until 2027, so 2026 provisions and returns rest on interim IRS notices issued through 2025 and February 2026.
- Because CAMT is computed from adjusted financial statement income, pension marks, fair value swings, depreciation conformity and purchase accounting now drive tax expense.
- Positions built on notices raise the bar for ASC 740 uncertain tax position analysis and create retroactivity risk if 2027 rules differ.
- Document a reliance memo this quarter covering documentation standard, reserve posture, disclosure language and the audit committee briefing.
- Expanded rate reconciliation disclosure means CAMT volatility is now visible to investors, so tax, reporting and IR need one agreed narrative.
