A corporate spin-off distributes shares of a new (or subsidiary) company to existing shareholders of the parent. Unlike a simple stock split, your total cost basis is usually split between the parent ticker and the spun-off ticker using an issuer allocation percentage—not left entirely on the old shares. Brokers at Fidelity, Vanguard, Schwab, and E*TRADE often adjust covered lots automatically, but you still need the issuer’s Form 8937 / cost-basis worksheet when you sell either side.
Where basis shows up at sale: 1099-B basis adjustment basics. Account wrapper: Taxable brokerage account basics. Filing orientation: Filing taxes for beginners.
Spin-off vs split vs cash dividend
| Event | Share count | Cost basis | Typical tax event? |
|---|---|---|---|
| Forward stock split | Multiplies; per-share basis divides | Total basis unchanged | Usually no until sale |
| Tax-free spin-off (common educational case) | You receive new shares; parent share count may stay the same | Allocate total basis across parent + spinco per issuer % | Often nontaxable if IRS/issuer conditions met; confirm |
| Taxable spin-off / dividend of stock | New shares may be treated as a dividend | Basis rules follow the taxable characterization | May create current income |
| Cash dividend | Cash only | Basis unchanged (unless return of capital) | Usually taxable in taxable accounts |
Always read the issuer’s spin-off FAQ and IRS Form 8937 (Report of Organizational Actions Affecting Basis). Do not invent a 50/50 split because it “feels fair.”
How allocation usually works (educational pattern)
- Start with your pre-spin total basis in the parent lots (what you paid, adjusted for prior DRIP, splits, and return of capital).
- Apply the issuer’s allocation percentages (for example 88% parent / 12% spinco, or a formula based on opening trading prices).
- Multiply: new parent basis = old total × parent %; spinco basis = old total × spinco %.
- Divide by post-spin share counts to get per-share basis on each ticker.
- Holding periods for the spinco shares often tack to the parent holding period for capital-gains aging—confirm with the issuer notice and a preparer.
Brokers may show the adjustment weeks after the distribution. Export lot reports before and after so Form 1099-B matches your spreadsheet (Tax lot identification).
Worked example: $10,000 parent, 90% / 10% allocation
Casey bought 100 shares of ParentCo at $100 ($10,000 total basis) in a Schwab taxable account. ParentCo spins off SpinCo. The issuer’s Form 8937 says allocate 90% of basis to ParentCo and 10% to SpinCo. Casey receives 20 SpinCo shares (illustrative ratio).
| Ticker | Allocation | New total basis | Shares after | Per-share basis |
|---|---|---|---|---|
| ParentCo | 90% | $9,000 | 100 | $90 |
| SpinCo | 10% | $1,000 | 20 | $50 |
Months later Casey sells all 20 SpinCo shares for $1,400. Gain is about $400 ($1,400 − $1,000) before commissions—not $1,400 of “free” proceeds with zero basis. The remaining ParentCo lots keep $9,000 of basis.
If Casey had left parent basis at $100/share and treated SpinCo as $0 basis, the 1099-B / Form 8949 picture would overstate gain on SpinCo and understate gain on a later ParentCo sale.
Practical habits
- Download the issuer Form 8937 and any broker corporate-action notice the week of the spin.
- Recompute one lot by hand; then trust (and spot-check) the broker’s adjusted lots.
- When selling only the spinco, use the allocated basis—not zero and not the pre-spin parent price.
- Keep pre-spin confirms; they still prove acquisition date for holding-period tacking.
- Watch for cash in lieu of fractional spinco shares; that cash can be a small taxable sale (Merger cash-in-lieu basics).
- Index-fund holders: the fund’s capital-gain and basis mechanics inside the wrapper still dominate (Investing basics for beginners).
Checklist
- Confirm whether the issuer describes the spin as nontaxable, partially taxable, or taxable.
- Record allocation percentages from Form 8937—not a guess.
- Split total basis across parent and spinco; recompute per-share figures.
- Reconcile broker lot reports before year-end.
- Flag fractional cash-in-lieu as possible 1099-B proceeds.
- At filing, match both tickers on Form 1099-B to the allocated history (1099-B basis adjustments).
Educational only. Not tax, legal, or investment advice. Spin-off tax treatment and basis allocation are technical and deal-specific; verify with current IRS publications, the issuer’s Form 8937, Form 8949 / Schedule D instructions, and a qualified tax professional.