Zero-Cost Collar Financing Tradeoffs
A zero-cost collar funds a protective put by selling a call for the same premium, but "zero cost" only refers to the upfront cash — it still costs upside, and the strikes that balance the premium shift with volatility skew.
A holder who wants downside protection but doesn't want to pay for it outright can buy a put and sell a call whose premiums exactly offset, so no cash changes hands upfront — a zero-cost collar. It reads like a free hedge, but the "zero" only describes the day-one cash flow.
A zero-cost collar doesn't eliminate cost, it converts the cost of protection into a cap on upside — and the strike where that cap sits depends on the volatility skew, since puts and calls at equal distance from spot rarely have equal premiums.
Drag the put and call strikes above and watch the premiums move: to keep the trade zero-cost, moving the put strike further from spot (cheaper protection) requires moving the call strike closer to spot (giving up more upside) to keep the premiums balanced, and vice versa. Because equity index skew usually makes out-of-the-money puts more expensive than equally-distant calls, a true zero-cost collar on an index typically has to set the call strike closer to spot than the put strike is, capping upside more tightly than the downside protection it provides.
This asymmetry means a "10% downside, 10% upside" collar is rarely actually free — pricing it zero-cost against real skew usually pushes the cap to something like 6–7% upside for that same 10% downside protection. Investors who assume symmetric caps and floors from the collar's stated strikes without checking the skew-adjusted zero-cost strikes routinely misjudge how much upside they're actually giving away.
Practice in interviews
Further reading
- Natenberg, Option Volatility and Pricing (ch. 20)