EXPIRY WEEK: GAMMA, THE PIN, THE WALL

The last week of a spread’s life is a different instrument: values cliff instead of slope, delta races, and a three-cent close can separate your two legs over a weekend. Stage 6’s gamma and Stage 7’s pin with the training wheels off — and the course’s wall: nothing rides into expiry day. A spread approaching expiry is a plane on final approach: at altitude, weeks out, the controls are gentle and a degree of heading is a suggestion; close to the ground, the same degree is the whole landing. Nothing about the aircraft changed — the distance to the hard surface did. Gamma is that shrinking distance. Near the strikes, near the deadline, small moves in SPY stop nudging your spread’s value and start slamming it between its two flat states — worth everything or worth nothing — with the pin zone as the patch of runway where you cannot tell which state you’re in until the weekend’s paperwork lands. Professional pilots don’t improvise on final; they fly a stabilised approach or they go around early. This course’s wall — out a week early on debits, out before expiry day on credits — is the go-around, briefed on the ground.

EXPIRY WEEK · STAGE 8 · LESSON 5

THE TAKEAWAYS

• The cliff, tabulated (the graphic draws it): the 765/760 spread’s value at expiration across SPY closes — 770: 0.00 · 766: 0.00 · 765: 0.00 · 764: 1.00 · 763.96: 1.04 · 763: 2.00 · 762: 3.00 · 761: 4.00 · 760: 5.00 · 755: 5.00. Between the strikes the value is simply 765 − SPY. Mid-life, the same $2 slide (764 → 762) moves the spread by much less — both legs still carry time value and their deltas only partly engage (the exact mid-life figure belongs to that day’s chain; the shape is the lesson). At expiry it is the full $200. The position’s personality inverts across its life: the ‘quiet’ trade of week two is a binary coin by the Friday of week seven, its delta able to cross the whole width’s exposure in a single afternoon.
• Theta’s last-week bargain, refused: yes, an out-of-the-money credit spread’s remaining value decays toward zero by Friday, and holding ‘a few more days’ harvests what’s left — say the spread marks 0.30 on Wednesday: $30 of harvest. Against it: the same Wednesday, a slide to a 762 close re-marks the spread at 3.00 — a $270 swing against you, accepted in exchange for collecting $30. The final week’s theta is real money, priced against cliff risk, and the course declines the trade without embarrassment: some premiums are wages for carrying exactly the risk this course exists to avoid, and recognising the wage doesn’t oblige you to earn it.
• Contrary instructions — the pin is unknowable, not merely unlikely: holders may instruct their clearing member NOT to exercise an in-the-money option, or TO exercise an out-of-the-money one (the OCC’s contrary-exercise mechanism, Rule 805(b)) — for reasons of their own: a stock position elsewhere, a hedge to flatten, a tax lot. So ‘SPY closed $0.04 above my strike, I’m safe’ is not a fact available to you on Friday night. Assignment is determined by the whole market’s instructions and allocated after the close (Lesson 6 walks the machinery). The only state in which a spread cannot be pinned is closed.
• The debit side’s wall sits earlier for a reason: a debit vertical’s remaining value in its final week is mostly hope priced by gamma — Stage 7’s build exited on Nov 23, seven days out, sacrificing the last slice of its $58 cap to leave while the spread still had two-sided value and a functioning market in it. Calendar rules in this course are structure-specific and written on the plan card at entry, because ‘I’ll decide when we get there’ is how positions meet Friday.

WORKED EXAMPLE — STEP BY STEP

1. Rebuild the cliff from the contract itself — no chain required, because expiry value is definition, not data: the 765/760 put spread at expiration is worth max(0, 765 − SPY) − max(0, 760 − SPY): 0.00 at 765 and above, rising $100 per point through the band, 5.00 at 760 and below. Read the graphic’s table until the shape is physical: flat, cliff, flat.
2. Attach the calendar: this spread was sold Oct 9 for the Nov 30 expiry — 52 days. In week one, a $2 slide from 764 to 762 changes the spread’s value modestly: both legs carry time value, and the structure’s delta is a fraction of the width. In the final week the same slide is worth the full $200 swing. Same strikes, same width, same ticker — the expiry clock, not the market, changed the instrument. (The mid-life figure is illustrative shape, labeled as such; the expiry column is exact by definition.)
3. Walk the pin once more, slowly (Stage 7’s numbers, the machinery named): Friday’s close is 764.97. The 765 put is $0.03 in-the-money — past the OCC’s $0.01 threshold — and is exercised by exception unless its holder filed a contrary instruction; the 760 put is out-of-the-money and expires, unless ITS holder chose to exercise it (someone might, to flatten a stock hedge). You learn your assignment state from your broker after processing — over the weekend. Monday’s position in the assigned case (Stage 7): long 100 shares at 765 with the floor gone, ≈ −$1,396 at a 750 open. Every clause of that paragraph is a reason the course’s spread is already closed.
4. Price the wall: exiting this spread on the Thursday before expiry — or at its earlier doors — costs the two-leg closing toll (Stage 7’s estimate for these sizes: a few dollars to perhaps twenty) plus whatever the doors’ marks dictate that day. Across a 30-trade sample the wall’s lifetime cost is on the order of a few hundred dollars of friction — against a single pin leak of ≈ $1,000 beyond the printed max. Insurance arithmetic doesn’t get cleaner than that, and the course pays it without re-voting.
5. Write the wall onto every plan, in dates, on entry day: (a) debit structures — time exit = expiry minus seven days (Lesson 6’s Nov 23 for Nov 30); (b) credit structures — hard close no later than the session before expiry day, with the doors usually firing earlier; (c) any SPY ex-date inside the final two weeks pulls a short call’s close earlier still (Stage 7’s distribution trap). Three dates on the card before the ticket exists.

WHAT CHANGED AT EXPIRY — THE GREEKS, ONE LAST TIME

Stage 6’s cast, in expiry-week costume. GAMMA: maximal near the strikes — the spread’s delta can traverse its whole range across a few points, which is the cliff. THETA: maximal too — the remaining extrinsic value burns to zero by Friday, tempting holders in both directions (credit sellers harvesting, debit buyers bleeding); the burn is the sound of the cliff forming. DELTA: no longer a probability-flavoured estimate you can lean on — inside the band at expiry it is a step function wearing a smooth disguise until the final hours. VEGA: nearly gone — IV can spike and the spread barely notices, because almost no time remains for volatility to act on; expiry week is the one week the IV lesson is silent. The summary worth memorising: a spread’s Greeks all sprint toward their expiry values at different speeds, and the trader’s information degrades exactly as the stakes concentrate. Systems that exit before this week aren’t being timid — they’re declining a game whose rules change hourly, in favour of one they’ve already priced.

COMMON BEGINNER MISTAKES

• Harvesting the last slice: holding an out-of-the-money credit spread into expiry week for its final $30 while standing a $270 cliff-swing away from one bad afternoon.
• Reading Friday’s close as a verdict (‘$0.04 above my strike — safe’). Contrary instructions (OCC Rule 805) mean assignment isn’t knowable from the close; only a closed spread is un-pinnable.
• Using one calendar rule for both families. Debit walls sit a full week out, because debit value dies there; credit walls are the day before expiry at the latest — for reasons priced in this lesson, not by symmetry.
• Forgetting the ex-date inside expiry week: a short call into SPY’s quarterly distribution is an assignment candidate regardless of the pin (Stage 7) — the calendar has two traps, and the wall must clear both.

CHECK YOURSELF

DO IT — DRAW YOUR SPREAD’S CLIFF AND ITS WALL

For one open paper spread (or Stage 7’s credit spread), compute its full expiry-value table by hand, from the definition — every dollar from $3 above the short strike to $3 below the long strike. Then mark on the calendar: the time-exit date this course’s wall assigns the structure, any SPY ex-date inside its life, and the last session it may exist under your plan. Under the table, write the harvest refusal in one line: ‘The most this spread can pay me in its final week is $___; the cliff can take $___ in the same week; I choose the wall.’ Paper only. Gate artefact — the lifecycle simulation in Lesson 7 starts from this table.