7.5 Corporate Actions and Basis Adjustments

Corporate Action Adjustments on Cost Basis

Corporate actions alter the capital structure of an issuer and require back-office operations to execute mandatory adjustments to customer position quantities, per-share cost bases, and holding periods.

1. Forward Stock Splits

In a forward stock split, the issuer increases the total number of outstanding shares to lower the per-share market price:

• Share Quantity: Increases by the split ratio (e.g., a 3-for-1 split multiplies shares by 3; a 3-for-2 split multiplies shares by 1.5).
• Per-Share Basis: Decreases in inverse proportion to the split ratio.
• Total Basis: Remains unchanged.
• Holding Period: Carries over from original acquisition date.
• Example: An investor owns 200 shares purchased at $90 ($18,000 total basis). Following a 3-for-1 stock split, the investor holds 600 shares (200 shares * 3) with an adjusted cost basis of $30 per share ($90 / 3). Total basis remains $18,000.

2. Reverse Stock Splits

In a reverse stock split, the issuer reduces the total number of outstanding shares to increase the market price per share:

• Share Quantity: Decreases by the reverse split ratio (e.g., a 1-for-5 reverse split divides shares by 5).
• Per-Share Basis: Increases in inverse proportion.
• Total Basis: Remains unchanged.
• Example: An investor owns 1,000 shares purchased at $4 ($4,000 total basis). Following a 1-for-10 reverse stock split, the investor holds 100 shares (1,000 shares / 10) with an adjusted cost basis of $40 per share ($4 * 10). Total basis remains $4,000.

3. Stock Dividends

A stock dividend distributes additional shares to shareholders instead of cash:

• A qualifying nontaxable stock dividend can be treated similarly to a split; some stock distributions are taxable depending on their terms.
• Determine the issuer’s tax classification before adjusting basis.
• The original total cost basis is allocated across the expanded total share count.
• Example: An investor owns 500 shares purchased at $44 ($22,000 total basis). The company declares a 10% stock dividend, delivering 50 additional shares. The investor now owns 550 shares with an adjusted cost basis of $40 per share ($22,000 / 550).

4. Corporate Spinoffs

In a qualifying tax-free spinoff, a parent distributes subsidiary shares:

• Basis Allocation Rule: The customer's original cost basis in the parent company must be allocated between the parent shares and the newly distributed subsidiary shares based on their relative fair market values (FMV) on the distribution/ex-date.
• Holding Period: The holding period of the parent shares transfers to the spun-off subsidiary shares.
• Example: An investor holds 100 shares of Parent Corp with a total cost basis of $10,000. Parent Corp spins off SpinCo. On the ex-date, Parent Corp trades at $80 per share ($8,000 total FMV) and SpinCo trades at $20 per share ($2,000 total FMV). Total combined value is $10,000:
  • Parent Corp represents 80% of value ($8,000 / $10,000); its basis becomes $8,000 ($80 per share).
  • SpinCo represents 20% of value ($2,000 / $10,000); its basis becomes $2,000 ($20 per share).

5. Mergers & Acquisitions: Cash vs. Stock

• Cash Mergers: The target company is acquired entirely for cash. This is a fully taxable transaction. Target shareholders surrender shares and receive cash proceeds; the broker-dealer reports gross proceeds on Form 1099-B, triggering immediate capital gain or loss.
• Stock-for-Stock Mergers (Tax-Free Reorganizations under IRC Section 368): Target shareholders surrender their shares in exchange for shares of the acquiring entity. No immediate capital gain or loss is recognized. The customer's cost basis and holding period in the target stock roll over into the newly received acquiring company stock.
• Cash in Lieu of Fractional Shares: When a stock merger calculation results in a fractional share, brokers distribute cash in lieu of fractional shares. This cash distribution is treated as a partial redemption and triggers taxable capital gain or loss reported on Form 1099-B.

Reconciliation After an Action

Reconcile the issuer/agent announcement, effective dates, tax characterization, new quantities and aggregate basis. For a nontaxable split, total basis should remain unchanged except for separately treated fractional-share cash. A doubled share balance with unchanged per-share basis would incorrectly double total basis.

Do not assume every stock distribution or merger is tax-free. Use issuer tax information and the transaction’s actual terms, preserve basis allocation and holding-period treatment, and review corrected information. Inform the tax-reporting team when an action changes covered-lot data after an initial statement was generated.

Sources checked 2026-10-20: FINRA statements, IRS Publication 550, IRS Form 1099-B instructions.