The old corporate AMT was repealed after 2017, but beginning with tax years after 2022, large corporations can face a new 15% Corporate Alternative Minimum Tax (CAMT) based on adjusted financial statement income (AFSI)—plus other “special taxes” like the 1% stock repurchase excise tax, BEAT, and the personal holding company (PHC) and accumulated earnings taxes. This guide translates the rules founders most often bump into—who’s covered, which forms, and planning moves. IRS+1

Why this matters (Problem → Agitate → Solution)

You formed a C-corp to scale or to pursue QSBS. But as you grow, book income can drive tax (CAMT), buybacks can trigger a 1% excise, payments to foreign affiliates can pull you into BEAT, and retaining too much cash can raise PHC/AET risk. Below is the playbook—federal only (we’ll use Texas only when a state comparison helps).

1) Where we are now: From “old AMT” to CAMT

  • Old corporate AMT repealed for tax years beginning after Dec. 31, 2017. IRS
  • The Inflation Reduction Act created a 15% CAMT on AFSI for large corporations starting with tax years after Dec. 31, 2022. IRS

Who is “large” for CAMT?

  • Generally, corporations with average annual AFSI > $1B (3-year lookback). For foreign-parented groups, a U.S. member can be in-scope with ≥ $100M U.S. AFSI if the global group also meets the $1B test. Compute and file on Form 4626. IRS+1

2025 interim relief you can actually use

  • Notice 2025-27 provides an interim simplified method to check CAMT applicability (temporarily testing at $800M and $80M instead of $1B/$100M) and grants estimated-tax penalty relief in certain cases while rules finalize. (It’s optional—use only if it helps.) IRS+1

Founder takeaway: If you’re anywhere near these thresholds—or part of a foreign-parented group—have your controller/CFO model AFSI vs. CAMT using Form 4626 instructions and the current notices. IRS

2) 1% Excise Tax on Stock Buybacks (IRC §4501)

A 1% excise tax applies to the fair market value of repurchased stock by covered corporations for repurchases after Dec. 31, 2022. Treasury/IRS issued regulations on how to report and pay (including netting rules and exceptions). If you’re doing redemptions, structured buybacks, or SPAC-style transactions, coordinate early with tax counsel. IRS

3) BEAT (Base Erosion and Anti-Abuse Tax) — IRC §59A

BEAT is a minimum tax aimed at corporations that make significant base-erosion payments to foreign related parties. It generally applies when average annual gross receipts ≥ $500M and the base-erosion percentage ≥ 3% (2% for certain financials). Compute on Form 8991. IRS+1

4) Personal Holding Company (PHC) Tax — IRC §541

A corporation that is both (i) closely owned (more than 50% by five or fewer individuals during the last half of the year) and (ii) has ≥ 60% PHC income (mostly passive) may owe a PHC tax on undistributed PHC income. It’s self-assessed on Schedule PH (Form 1120). IRS+1

5) Accumulated Earnings Tax (AET) — IRC §531

If a corporation accumulates earnings beyond the reasonable needs of the business to avoid shareholder-level tax, the IRS can impose a 20% tax on accumulated taxable income. The IRS Internal Revenue Manual explains the standard; the statute sets the 20% rate. (This is separate from PHC.) IRS+1

Filing & forms you’ll actually touch

  • Form 4626 (CAMT) & instructions (AFSI tests, consolidated group rules). IRS
  • Form 8991 (BEAT) & instructions (base-erosion payments, percentage, modified taxable income). IRS
  • Schedule PH (Form 1120) (PHC tax). IRS
  • Form 1120 instructions reference these “other taxes” and where they flow on the return. IRS

Planning checkpoints for founders (2025)

  1. Screen for CAMT early. If consolidated AFSI could approach the thresholds—or you’re foreign-parented—use Form 4626 rules and consider the Notice 2025-27 interim method for scoping and estimates. IRS+1
  2. Buybacks: Before a board approves repurchases/redemptions, model the 1% excise and any exceptions; ensure tracking to compute net repurchases correctly. IRS
  3. Related-party cross-border flows: Map intercompany charges, withholdings, and BEAT exposure; run Form 8991 sensitivities as revenue scales. IRS
  4. Cash piles: If you’re primarily passive-income or closely held, monitor PHC tests. If you’re accumulating cash, document reasonable business needs (expansion, R&D, working capital) to mitigate AET risk. IRS+1
  5. Texas note: Texas has no corporate income tax, but it does have a franchise (margin) tax; that’s state—not covered by these federal special taxes. (We use Texas only when a state comparison helps.)

Bottom line

Most startups won’t hit CAMT/BEAT right away, but growth, acquisitions, or group structures can change the answer quickly. Bake these screens into your quarterly close so you’re never surprised at filing time.

Want a fast CAMT/BEAT/PHC/AET screen tied to your 2025 board calendar? Finpilot360 can model the exposures and set triggers.