If your corporation has averaged more than $1 billion in adjusted financial statement income (AFSI) over the prior three tax years, you must file IRS Form 4626 to calculate the Corporate Alternative Minimum Tax (CAMT). The form applies a 15% minimum tax on the book income of the largest U.S. corporations and was revived by the Inflation Reduction Act of 2022 under Internal Revenue Code §55.
The CAMT only hits roughly 150 of the largest U.S. corporations, according to the Joint Committee on Taxation, yet every C-corporation must run the test each year to confirm it is not an applicable corporation. Missing the filing can trigger accuracy-related penalties under IRC §6662 of up to 20% of any underpayment, plus interest that compounds daily.
Here is what you will learn in this guide:
- 📋 Who qualifies as an applicable corporation and must file Form 4626
- 🧮 How to compute AFSI line-by-line with every adjustment under IRC §56A
- 💰 How to claim the CAMT Foreign Tax Credit and general business credits
- ⚠️ The most common Form 4626 mistakes that draw IRS notices
- 🧾 Three real-world filing scenarios with dollar-by-dollar walkthroughs
What Is IRS Form 4626?
Form 4626, Alternative Minimum Tax — Corporations is the federal worksheet that applicable corporations use to compute the 15% Corporate Alternative Minimum Tax. The form was retired in 2018 after the Tax Cuts and Jobs Act repealed the old corporate AMT, but it returned for tax years beginning after December 31, 2022. The reinstated version looks similar in name only because the new CAMT is built on book income rather than taxable income.
Every C-corporation, including foreign corporations with U.S. effectively connected income, must complete at least Part I of Form 4626 each year. Part I is the applicability test that determines whether the corporation crosses the AFSI threshold. If the test fails, the corporation files only the first page; if the test passes, the corporation completes Parts II through IV.
The IRS released the final 2024 instructions for Form 4626 in late 2024, and the September 2024 proposed CAMT regulations added more than 600 pages of operational rules. Tax preparers should expect the 2025 form to closely mirror the 2024 layout while integrating any final regulations issued before the 2026 filing season. The new structure makes Form 4626 one of the most complex schedules attached to Form 1120.
Who Must File Form 4626?
Every U.S. C-corporation must complete the applicability test on Form 4626 each year, even if it clearly does not owe CAMT. The IRS confirmed this filing requirement in the 2024 form instructions, and skipping the form is treated as a missing schedule that can void the substantial-authority defense to penalties. The rule prevents corporations from self-selecting out of CAMT without documentation.
A corporation is an applicable corporation under IRC §59(k) if its average annual AFSI exceeds the relevant threshold over any three consecutive prior tax years ending after 2021. Once a corporation crosses the line, it stays applicable in future years unless an ownership change or a sustained AFSI drop triggers an IRS-approved exit under the proposed regulations.
The $1 Billion Domestic Threshold
A standalone U.S. corporation or a U.S.-parented group is an applicable corporation if average AFSI exceeds $1 billion over the three-year testing period. The threshold is measured before applying CAMT-specific adjustments such as the financial-statement net operating loss deduction. The rule appears in IRC §59(k)(1)(B).
The consequence of crossing the line is steep because every dollar of AFSI above the exemption amount is exposed to the 15% tentative minimum tax. A common misconception is that crossing $1 billion in one year triggers CAMT; in reality, the test uses a three-year rolling average, so a single spike in book income may not be enough. Companies near the threshold should model AFSI for at least five forward years.
The $100 Million Foreign-Parented Threshold
A U.S. subsidiary of a foreign-parented multinational group is an applicable corporation when the U.S. members average more than $100 million in AFSI and the worldwide group averages more than $1 billion in AFSI. This dual test, found at IRC §59(k)(2), captures inbound corporations that would otherwise dodge CAMT through low U.S. earnings.
The consequence of misapplying this test is that the foreign parent’s AFSI counts in full for the worldwide test, which can pull a small U.S. subsidiary into CAMT exposure. A real-world example is a Japanese auto manufacturer with $50 billion of global AFSI and $250 million of U.S. AFSI; the U.S. subsidiary becomes an applicable corporation. Many in-house tax teams overlook the worldwide-group rule and underreport applicability.
The Aggregation Rules
IRC §59(k)(1)(D) requires aggregation of all entities under common control within the meaning of IRC §52(a) and §52(b). Brother-sister groups, partnerships, and disregarded entities all roll up to the parent for purposes of the AFSI test. Aggregation prevents a corporation from splitting its operations into smaller subsidiaries to dodge the threshold.
The penalty for ignoring aggregation is a back-assessment of CAMT plus interest and penalties. A common misconception is that controlled foreign corporations (CFCs) are excluded; in fact, IRC §56A(c)(2)(C) requires inclusion of pro-rata CFC AFSI for U.S. shareholders. The aggregation rules are the single most error-prone area of CAMT compliance.
Walking Through Form 4626 Line-by-Line
The 2024 version of Form 4626 has four parts and 26 numbered lines, plus several lettered sub-lines on Part II. The structure follows the statute: applicability, AFSI computation, foreign tax credit, and final CAMT. Use the IRS draft instructions to match line numbers when working from a prior-year return.
Part I — Applicability Determination
Part I asks the corporation to compute its three-year average AFSI and compare it to the threshold. Line 1 captures AFSI for the current and two prior years. Line 2 divides by three to produce the average. Line 3 asks whether the average exceeds $1 billion (or $100 million for foreign-parented U.S. subsidiaries).
The consequence of answering No on Line 3 is that the corporation stops here, signs the form, and attaches it to its Form 1120. Answering Yes triggers the full CAMT computation. A common mistake is using GAAP net income directly without making the §56A book-to-AFSI adjustments before averaging.
Part II — Adjusted Financial Statement Income
Part II begins on Line 4 with the corporation’s net income or loss from its applicable financial statement (AFS) as defined in IRC §451(b)(3). The AFS hierarchy puts SEC 10-K filings first, audited GAAP statements second, and audited IFRS statements third. Lines 5 through 22 then list the dozens of statutory adjustments.
Key adjustments include consolidation conformity on Line 5, partnership distributive share on Line 6, controlled foreign corporation pickups on Line 7, effectively connected income for foreign corporations on Line 8, depreciation conformity to IRC §168 on Line 12, qualified wireless spectrum amortization on Line 13, and pension and defined-benefit adjustments on Line 14. Line 22 produces the financial-statement net operating loss (FSNOL) deduction, capped at 80% of pre-NOL AFSI under IRC §56A(d).
The consequence of misclassifying an adjustment is double-counting income or losing a deduction, and the IRS examination teams have flagged depreciation conformity as a top audit issue. A real-world example is a manufacturer that takes 100% bonus depreciation for regular tax but must reverse the book-tax difference on Line 12 of Form 4626. The reversal can swing AFSI by hundreds of millions of dollars.
Part III — CAMT Foreign Tax Credit
Part III computes the CAMT Foreign Tax Credit (CAMT FTC) under IRC §59(l). Line 23 captures foreign income taxes paid or accrued by the corporation and its CFCs, limited to taxes reflected on the AFS. Line 24 applies the limitation that prevents the credit from exceeding the foreign portion of tentative minimum tax.
The consequence of overstating the CAMT FTC is a hard-dollar tax disallowance plus penalties, because the credit is the single largest reducer on the form. A common misconception is that the regular FTC and CAMT FTC are identical; they are not, because the CAMT FTC starts from book taxes rather than the regular §901 FTC pool. Tax departments should maintain a separate CAMT FTC working file.
Part IV — Tentative Minimum Tax and CAMT
Part IV calculates the final tax. Line 25 multiplies AFSI (after FSNOL) by 15% to produce the tentative minimum tax. Line 26 subtracts the CAMT FTC and then compares the result to the regular tax plus the Base Erosion and Anti-Abuse Tax (BEAT) under IRC §59A.
If the tentative minimum tax exceeds the regular tax plus BEAT, the difference is the CAMT owed and flows to Schedule J of Form 1120. The consequence of underreporting on Line 26 is that the IRS will recompute under IRC §6213 and assess the deficiency. Corporations may also generate a CAMT credit carryforward under IRC §53 usable against future regular tax.
The Simplified Method Safe Harbor
The IRS issued a simplified method safe harbor in Notice 2023-7 and refined it in the September 2024 proposed regulations. The safe harbor lets a corporation skip the full AFSI computation if its unadjusted AFS income is below $500 million (domestic) or $50 million (foreign-parented U.S. subsidiary) on a three-year average basis. The thresholds are half of the statutory thresholds and are meant to give clearly-not-applicable corporations a paperwork shortcut.
The consequence of relying on the safe harbor incorrectly is a back-assessment plus penalties because the safe harbor is self-certifying and the IRS can audit the underlying numbers for six years. A real-world example is a private equity portfolio company at $480 million of book income that uses the safe harbor; if a partnership pickup pushes the figure above $500 million, the safe harbor fails. Corporations should document the safe harbor calculation in their tax workpapers.
Three Real-World Filing Scenarios
The following scenarios show how Form 4626 plays out for three common corporate profiles. Each scenario uses round numbers for clarity and assumes the 2025 tax year filed in 2026. The scenarios draw on guidance in Notice 2023-64.
Scenario 1: A Domestic Tech Company Crosses the Line
MegaCloud Inc., a publicly traded U.S. software company, reports three-year average AFSI of $1.4 billion. The company has $1.6 billion of AFSI in 2025 after adjustments, and $200 million of regular tax liability after credits. MegaCloud has no foreign operations and no CAMT FTC.
| Form 4626 Step | Result for MegaCloud |
|---|---|
| Part I applicability test | Applicable — average AFSI > $1B |
| AFSI after adjustments | $1.6 billion |
| Tentative minimum tax (15%) | $240 million |
| Regular tax + BEAT | $200 million |
| CAMT owed (Line 26) | $40 million |
Scenario 2: A Foreign-Parented U.S. Subsidiary
AutoGlobal USA, the U.S. subsidiary of a German auto parent, has three-year average U.S. AFSI of $180 million and the worldwide group has $40 billion. The U.S. subsidiary has $250 million of AFSI in 2025 and pays $30 million of regular tax. The foreign parent’s CFC structure produces $12 million of CAMT FTC.
| Form 4626 Step | Result for AutoGlobal USA |
|---|---|
| Worldwide test | Applicable — group AFSI > $1B |
| U.S. AFSI test | Applicable — U.S. AFSI > $100M |
| Tentative minimum tax (15% × $250M) | $37.5 million |
| Less CAMT FTC | ($12 million) |
| Net minimum tax | $25.5 million |
Scenario 3: A Private Equity Portfolio Company Uses the Safe Harbor
Brookline Foods Corp., a private equity-owned snack manufacturer, reports three-year average unadjusted AFS income of $420 million. The company has no foreign operations and no controlled partnerships. Brookline elects the simplified method safe harbor under Notice 2023-7.
| Form 4626 Step | Result for Brookline Foods |
|---|---|
| Three-year average AFS income | $420 million |
| Safe harbor threshold | $500 million |
| Applicability conclusion | Not an applicable corporation |
| CAMT owed | $0 |
| Filing requirement | Part I only, with safe harbor box checked |
Three Named Examples of Filers
Example 1 — Patricia Chen, CFO of NorthBay Semiconductors. Patricia inherits a CAMT-applicable corporation with $2 billion of AFSI and $400 million of bonus depreciation timing differences. She uses IRC §56A(c)(13) to claim the depreciation conformity adjustment, which lowers AFSI to $1.6 billion. The savings cut tentative minimum tax by $60 million.
Example 2 — Marcus Reyes, Tax Director at Pacific Renewable Holdings. Marcus oversees a U.S. solar developer with $1.3 billion of AFSI and large §48 investment tax credits. Under the Inflation Reduction Act, the credits remain creditable against CAMT, so Marcus reduces CAMT liability by $35 million through the general business credit.
Example 3 — Dr. Elena Petrov, Controller at BioGenix Therapeutics. Elena’s company is a biotech with three-year average AFSI of $980 million and erratic earnings. She documents the safe harbor on the workpapers and files only Part I of Form 4626. The decision saves about 200 hours of tax-department time and avoids a $200,000 outside-advisor fee.
Mistakes to Avoid
Even sophisticated tax departments stumble on Form 4626. The IRS Large Business and International Division has signaled that CAMT is a coordinated audit issue. Avoid these errors:
- Skipping Part I when AFSI is low. Every C-corporation must file at least Part I, and skipping it can void the reasonable-cause defense for penalties.
- Using GAAP net income unadjusted. Plugging book income directly into Line 4 without §56A adjustments overstates or understates AFSI by hundreds of millions.
- Ignoring the worldwide group test. Foreign-parented U.S. subsidiaries miss the dual test and underreport applicability.
- Misapplying §52 aggregation. Brother-sister groups and disregarded entities must be combined; failure triggers back-assessments.
- Confusing regular FTC with CAMT FTC. The two credits use different starting points and limitations under IRC §59(l).
- Forgetting partnership pickups. A corporate partner must include its distributive share of partnership AFSI under IRC §56A(c)(2)(D).
- Overlooking pension and OPEB conformity. Defined-benefit plan adjustments are mandatory and reverse most book mark-to-market noise.
- Using the wrong AFS. The hierarchy under §451(b)(3) puts SEC filings first; switching to a non-priority AFS invites recharacterization.
- Missing the FSNOL 80% cap. The financial-statement NOL is capped at 80% of pre-NOL AFSI, and exceeding the cap triggers a deficiency.
- Failing to track CAMT credit carryforwards. The credit under IRC §53 is valuable in future profitable years and must be tracked annually.
Do’s and Don’ts of Form 4626
The CAMT is unforgiving because it sits on top of the regular tax system. Practitioners should treat the form as a separate compliance project rather than an add-on schedule. Follow these rules:
- Do maintain a separate AFSI ledger because the IRS expects audit-ready workpapers under IRC §6001.
- Do model AFSI five years forward because applicability is sticky once triggered.
- Do coordinate with the financial-reporting team because every adjustment ties to the audited AFS.
- Do review CFC AFSI quarterly because foreign book swings can flip applicability.
- Do document safe harbor calculations because the IRS can examine them for six years.
- Don’t treat CAMT as identical to old-AMT because the bases differ entirely.
- Don’t rely solely on tax software because most engines still struggle with §56A adjustments.
- Don’t ignore proposed regulations because REG-112129-23 signals the IRS audit posture.
- Don’t forget BEAT layering because BEAT is added to regular tax in the Line 26 comparison.
- Don’t assume the threshold drops because the $1 billion floor is statutory and not indexed for inflation.
Pros and Cons of CAMT Compliance
CAMT creates new compliance burdens, but it also creates planning opportunities for credits and timing. Weigh both sides:
- Pro: General business credits, including R&D and renewable energy credits, remain usable against CAMT.
- Pro: The CAMT credit carryforward under IRC §53 creates future tax assets.
- Pro: Depreciation conformity under §56A(c)(13) preserves the value of bonus depreciation.
- Pro: The safe harbor cuts paperwork for clearly-not-applicable corporations.
- Pro: CAMT planning improves overall book-tax discipline and audit readiness.
- Con: Compliance costs can run into the millions for first-year applicable corporations.
- Con: AFSI volatility makes effective-tax-rate forecasting difficult under ASC 740.
- Con: Foreign tax credit limits are tighter than under regular tax.
- Con: Aggregation rules can pull small U.S. subsidiaries into CAMT.
- Con: Penalties for under-reporting compound quickly under IRC §6662.
Filing Deadlines and Estimated Payments
Form 4626 attaches to the corporation’s Form 1120, which is due on the 15th day of the fourth month after year-end for most calendar-year corporations. Corporations may extend by filing Form 7004 for an additional six months, but the extension does not delay payment. CAMT must be paid through the normal estimated tax system under IRC §6655.
The IRS waived estimated tax penalties for CAMT for tax years that began before January 1, 2024, in Notice 2024-33, but the waiver has expired for the 2025 tax year. Underpayment of estimated CAMT now triggers the standard penalty under IRC §6655. Corporations should integrate CAMT into quarterly estimated-tax projections beginning with the first quarter of the year.
The consequence of missing an estimated payment is interest plus a non-deductible penalty that increases as the underpayment ages. A common misconception is that CAMT can be paid only at year-end; in fact, it follows the same quarterly schedule as the regular corporate tax. Tax departments should reset their estimated-tax models to include AFSI projections.
Recent Guidance and Court Activity
The Treasury and IRS have issued more than a dozen pieces of CAMT guidance since 2022. The most consequential are Notice 2023-7 on initial transition rules, Notice 2023-64 on AFSI computation, Notice 2024-10 on CFC dividends, and the September 2024 proposed regulations. Final regulations are expected before the end of the 2026 filing season.
Court activity has begun to develop. In Edison International v. Commissioner, the corporation challenged the depreciation conformity rule as inconsistent with the statute, although the case is still pending. The U.S. Chamber of Commerce has also filed comments arguing that several proposed-regulation provisions exceed Treasury authority. The consequence of pending litigation is that some Form 4626 positions may need to be revisited in amended returns.
A common misconception is that proposed regulations are not binding; under IRC §7805 and the Loper Bright Enterprises v. Raimondo decision, taxpayers may rely on proposed regulations but the IRS may challenge any inconsistent position. Tax positions should be documented with substantial-authority memoranda. The CAMT regulatory landscape will keep changing through at least 2027.
State Tax Considerations
Most states do not conform to CAMT, but a handful piggyback on federal taxable income in ways that can pull CAMT into the state base. California decouples from CAMT under California R&TC §23036, meaning a CAMT liability does not flow into the California minimum franchise tax. New York likewise decouples through its Article 9-A corporate franchise rules.
The consequence of missing a state conformity nuance is a state-level under- or over-payment that may not be caught for years. A real-world example is a Texas-based corporation that does not owe state income tax but still must reflect federal CAMT on the Texas franchise tax report margin calculation. Multistate filers should run a state-by-state conformity matrix each year.
A common misconception is that decoupling means the state ignores CAMT entirely. In fact, even decoupling states often require an addback or modification on the state return to back out the federal CAMT effect. State controllers should coordinate with federal preparers to align disclosures.
FAQs
Do all C-corporations need to file Form 4626?
Yes. Every U.S. C-corporation must complete the Part I applicability test on Form 4626 each year, even if the corporation clearly does not owe CAMT, per the 2024 IRS instructions.
Is Form 4626 the same as the old corporate AMT form?
No. The reinstated 2023 Form 4626 uses adjusted financial statement income rather than the prior taxable-income-based AMT, so the calculation, thresholds, and credits are entirely different from the pre-2018 version.
Does CAMT apply to S-corporations or partnerships?
No. CAMT applies only to C-corporations under IRC §55(a), but partnerships must report distributive-share AFSI to corporate partners that are themselves applicable corporations.
Can general business credits offset CAMT?
Yes. IRC §38(c)(6) allows general business credits, including R&D and renewable energy credits, to reduce the regular-tax base that is then compared to tentative minimum tax.
Is there a small-business exemption from CAMT?
Yes. Corporations whose three-year average AFSI is below the $1 billion statutory threshold are exempt and may also use the $500 million simplified method safe harbor under Notice 2023-7.
Does CAMT replace the regular corporate income tax?
No. CAMT is an alternative minimum tax that applies only when the 15% tentative minimum tax exceeds regular tax plus BEAT, so corporations always pay the higher of the two amounts.
Can CAMT generate a credit carryforward?
Yes. IRC §53 permits a CAMT credit carryforward to offset future regular tax in years when the corporation is not subject to CAMT, similar to the prior corporate AMT credit.
Do foreign corporations file Form 4626?
Yes. A foreign corporation with U.S. effectively connected income must compute AFSI on the ECI and file Form 4626 if its U.S. AFSI exceeds the $100 million threshold and the worldwide group exceeds $1 billion.
Are estimated tax payments required for CAMT?
Yes. CAMT follows the standard IRC §6655 quarterly estimated-payment regime, and the IRS waiver from Notice 2024-33 has expired for tax years after 2024.
Can a corporation amend a prior-year Form 4626?
Yes. A corporation may file an amended Form 1120-X within three years of the original due date to correct a Form 4626 error, including changes flowing from final CAMT regulations.
Is the simplified method safe harbor automatic?
Yes. A corporation may rely on the safe harbor without IRS pre-approval, but it must document the calculation in its workpapers and check the safe harbor box on Part I of Form 4626.
Does CAMT apply to RICs and REITs?
No. Regulated investment companies and real estate investment trusts are excluded from the definition of applicable corporation under IRC §59(k)(1)(E), and S-corporations are also excluded.
Related reading
- How to Fill Out IRS Form 1120-F (w/Examples) + FAQs
- How to Fill Out IRS Form 1120-W (w/Examples) + FAQs
- How to Fill Out IRS Form 1120-X (w/Examples) + FAQs
- How to Fill Out IRS Form 8858 (w/Examples) + FAQs
- How to Fill Out IRS Form 5471 (w/Examples) + FAQs
- How to Fill Out New York Form CT-3 (w/Examples) + FAQs
- How to Fill Out IRS Form 8300 (w/Examples) + FAQs