Synthetic Position

TL;DR: A synthetic position uses options to replicate the profit/loss profile of another instrument — most commonly, synthetic long stock (long call + short put at the same strike) behaves like owning 100 shares.

The most fundamental synthetic is synthetic long stock: buy a call and sell a put at the same strike and expiration. This combination has a delta of approximately 1.00 — meaning it moves dollar-for-dollar with the underlying stock, just like owning 100 shares. The mirror image, synthetic short stock, involves buying a put and selling a call at the same strike, creating a -1.00 delta position equivalent to shorting 100 shares. Put-call parity — the mathematical relationship that C - P = S - K (adjusted for rates and dividends) — is what makes synthetics possible. Any deviation from this parity creates an arbitrage opportunity that market makers quickly close.

Why use synthetics instead of just buying or selling stock? Capital efficiency is the primary reason. A synthetic long stock position requires margin only on the short put leg (similar to a cash-secured put), which can be significantly less than the full cost of 100 shares. This frees up capital for other positions. Synthetics also avoid certain costs and complications: no borrowing costs for synthetic short positions (unlike shorting stock), no dividend obligations, and potentially different margin treatment. Some traders use synthetics to avoid hard-to-borrow fees on stocks with limited short availability.

The risks of synthetic positions are real and distinct from holding actual stock. The short option leg carries assignment risk — if you have a synthetic long (short put), you could be assigned shares you weren't expecting, especially around ex-dividend dates. Synthetics also have expiration dates, unlike stock, so you need to roll positions forward to maintain exposure. The margin requirement on the short leg can change if the stock moves against you, potentially requiring additional capital. LeanOptions covers synthetic strategies in depth, including how to convert between synthetics and stock positions when market conditions change.