Unit 15 of 15 · Advanced

Verticals: the defined-risk building block

In one read

A vertical spread is a defined-risk options structure: you buy one option and sell another of the same type and expiry at a different strike, and the two strikes fence the outcome. Because the short leg helps pay for the long leg, the most you can lose and the most you can make are both fixed the moment the position is opened. A debit vertical costs money up front and reaches its maximum value if price travels to the far strike; a credit vertical collects money up front and keeps it if price stays away from the strikes. Either way the risk graph is a tilted step between two flat shelves — a known maximum loss on one side and a known maximum gain on the other. This unit builds that graph on a generic instrument as the defined-risk building block every larger structure is made from.

What a vertical spread is

A vertical spread is two options of the same type and the same expiry, at two different strikes — one bought, one sold. The name is literal: on an option chain the two strikes sit in the same expiry column, stacked vertically.

The reason to hold two legs instead of one is defined risk. A single long option has a known maximum loss but an open-ended payoff; a single short option has a known maximum gain but an open-ended loss. Pairing them fences both ends. The short leg you sell offsets part of the long leg you buy, so the position's maximum loss and maximum gain are both fixed at the moment you open it — you can read them off before anything happens.

Verticals come in two directions:

  • A debit vertical is a net purchase — you pay to put it on. It reaches its full value if price travels through to the far strike, and its most you can lose is what you paid.
  • A credit vertical is a net sale — you are paid to put it on. It keeps that credit if price stays on the safe side of the strikes, and its most you can lose is the distance between the strikes minus the credit.

Both describe the same shape from opposite sides.

A worked example

Take a generic instrument — call it GENCO — trading near 100. Build a debit call vertical: buy the 100 call and sell the 105 call, same expiry.

Suppose the net cost (the debit) is 2.00 per share of contract. Now the whole risk graph is already determined:

  • If GENCO finishes at or below 100, both calls expire worthless. You lose the 2.00 you paid — that is the maximum loss, a flat shelf.
  • If GENCO finishes at or above 105, the spread is worth its full 5.00 width (the 5-point gap between strikes). Subtract the 2.00 paid and the maximum gain is 3.00 — the other flat shelf.
  • Between 100 and 105, the value ramps from 0 up to 5 — the tilted step that connects the two shelves.

That two-shelves-and-a-ramp picture is the vertical's risk graph. A credit vertical is the mirror image: the same shelves, entered from the other side. None of this says whether to open one, or when to close it — it is the geometry of the structure, fixed and readable at entry.

See it in kestrel

Read a structure's behaviour off a real, recorded session instead of a payoff diagram alone:

npx kestrel.markets sim mean-reversion-range-fade

That runs a deterministic simulation over a generic range-bound session — managed licensed data, no wall time, no signup, no card — and prints a certified proof URL. Recompute the whole record on your own machine, byte for byte:

npx kestrel.markets certify https://kestrel.markets/proof/art_f576347572a410a52647cf90

Keep the tool one command away: drop the kestrel.markets MCP server into your client and the next session opens where this one left off — no account in between.

Recompute it

Every claim in this unit recomputes from a certified proof — no account, no card.

/proof/art_f576347572a410a52647cf90

Agent twin: /education/options/opt-spreads-vertical/content.md