Double Diagonal: Two Time Spreads with Different Strikes

Audit a double diagonal with executable four-leg pricing, strike-gap tails, front-expiration surface values, assignment branches, and signed Greek and roll ledgers.

For educational purposes only; not investment advice. Investing may result in loss.

Direct answer

A double diagonal is a market name, not a standardized contract definition. A common one-for-one version sells a nearer-dated put and call at inner strikes while buying later-dated put and call options at farther-out strikes on the same underlying. Each side differs in both strike and expiration. Another provider may use a different direction or ratio, so identify every signed leg, multiplier, deliverable, exercise style, and settlement method rather than relying on the label.

It is neither a one-expiration iron condor nor a double calendar with matching strikes. At the front expiration, the short obligations disappear or settle while the back options retain time value at different strikes. Therefore, no ordinary one-date payoff chart, fixed maximum gain, guaranteed profit range, or pair of breakevens is known at entry.

Structure and lifecycle

Lock put strikes K_PL<K_PS, call strikes K_CS<K_CL, and expirations T₁<T₂. Record every signed ratio, multiplier, live deliverable, currency, style, settlement, last-trade time, cutoff, and official settlement source.
State the common construction explicitly: sell P(K_PS,T₁), buy P(K_PL,T₂), sell C(K_CS,T₁), and buy C(K_CL,T₂). The inner strikes are geometry, not a guaranteed profit range.
Use synchronized executable quotes. Define signed opening net outflow per underlying unit as D_exec=A_PL2+A_CL2−B_PS1−B_CS1, positive for a debit and negative for a credit. Add fees and impact; a midpoint, last price, or theoretical mark is not an executed cost.
Keep pre-expiration and settlement ledgers separate. Before T₁, an executable four-leg close credit is C_close=B_PL2+B_CL2−A_PS1−A_CS1. At T₁, define front liabilities H_P=max(K_PS−S_set,0) and H_C=max(S_set−K_CS,0); intrinsic value cannot replace a short close ask before settlement.
If the surviving back options can be sold at bids B_PL2,T1 and B_CL2,T1, use V_T1=B_PL2,T1+B_CL2,T1−H_P−H_C. For quantity Q, compatible multiplier M, and fees and financing F, calculate P/L_T1=Q×M×(V_T1−D_exec)−F. For matched physical exercise, define tail gaps W_P=K_PS−K_PL and W_C=K_CL−K_CS; controlled tail comparisons are approximately Q×M×(−W_P−D_exec)−F and Q×M×(−W_C−D_exec)−F, not universal account maximum losses.
Scan spot and both volatility surfaces. A conditional breakeven solves V_t(S,surfaces)=D_exec+F/(Q×M) under a declared time, quote, and settlement scenario; there may be zero, two, or four roots. Normalize units and compute signed sensitivity as X_net=X_PL2+X_CL2−X_PS1−X_CS1; Delta, Gamma, Vega, and Theta can change sign.
Prewrite close-all, expire-or-close-fronts and retain the back strangle, roll-one-or-both-shorts, assignment, exercise, sell-long-and-trade-stock, and cash-settlement branches. Reconcile old realized P/L, roll cash, new obligations, residual back value, shares, strike cash, margin, funding, borrow, fees, and tax.

Four worked examples

Executable entry versus midpoint. A front 95 put is 1.40/1.50, its back 90 put is 1.75/1.85, a front 105 call is 1.30/1.40, and its back 110 call is 1.65/1.75. Thus D_exec=1.85+1.75−1.40−1.30=0.90 per share, or $90 with M=100. The midpoint debit is 1.80+1.70−1.45−1.35=0.70, or $70, which understates executable debit by $20. Four fees of $0.65 add $2.60, making initial cash outflow $92.60.
The same spot under different back surfaces. At T₁, let S_set=$100 and both front shorts expire worthless. If executable back bids are 0.60 and 0.70, then V_T1=1.30 and the fee-before result relative to D_exec=0.90 is +$40. If a volatility crush leaves bids of 0.35 and 0.40, then V_T1=0.75 and the result is −$15. Spot alone does not define a fixed profit area or breakeven.
Assignment, sale, and exercise are different ledgers. Let S_set=$115, so the short 105 call liability is $10 per share; the back 110 call bid is 7.25 and the back 90 put bid is 0.05. Then V_T1=0.05+7.25−10=−2.70, and relative to D_exec=0.90, P/L=(−2.70−0.90)×100=−$360. If the physical short call is assigned, the account receives $10,500 and owes 100 shares. Selling the back options for $725+$5 and buying shares for $11,500, then subtracting the $90 debit, also gives −$360. Exercising the back call instead gives $10,500−$11,000+$5−$90=−$585, which is $225 worse because it forfeits (7.25−5.00)×100=$225 of executable call time value.
Signed Greeks, term skew, and a roll ledger. Per-unit (Delta,Gamma,Vega,Theta) values are front put (−0.28,0.020,0.07,−0.05), back put (−0.20,0.010,0.12,−0.02), front call (0.28,0.020,0.07,−0.05), and back call (0.20,0.010,0.12,−0.02). With short fronts, long backs, and M=100, net values are Delta=0 shares, Gamma=−2 shares/$1, Vega=+$10 per volatility point, and Theta=+$6/day. Frozen-Greek Gamma P/L for a $3 move is 0.5×(−2)×3²=−$9. If front IV rises 4 points while back IV falls 3 points, the Vega approximation is (−0.07−0.07)×100×4+(0.12+0.12)×100×(−3)=−$128. Paying 0.45 to close both old shorts and receiving 1.20 for two new shorts creates a 0.75 roll credit. The old shorts realized 1.40+1.30−0.45=+2.25 per share, while the new 1.20 is cash against a new obligation, not profit.

Risk checklist

The strategy name may conceal different legs, directions, strikes, expirations, or ratios.
A wrong root, series, option type, strike, expiration, or sign changes the claim.
Quantities, multipliers, adjusted deliverables, and currencies may not match across legs.
Last-trade times, exercise cutoffs, time zones, and AM/PM settlement can differ.
American/European and physical/cash settlement mismatches alter the lifecycle.
Stale, asynchronous, midpoint, last, and model prices are not executable package values.
Partial fills, legging, routing, and rejected legs can create unintended exposure.
Front Gamma can dominate near T₁.
Front and back volatility, skew, and term structure can move independently.
Back-option quotes, models, and liquidity can fail when most needed.
Delta, Gamma, Vega, and Theta signs can change across spot and time.
Gaps, halts, and price limits can invalidate local or frozen-Greek analysis.
Early assignment depends on dividends, borrow, carry, and option extrinsic value.
Assignment does not automatically exercise or sell a back option.
Exercising a back option can destroy time value while locking in the strike gap.
Stock inventory, strike cash, and official settlement require separate ledgers.
Margin, buying power, collateral, and forced liquidation can exceed planned cash.
Borrow, dividend payments, funding, fees, impact, and tax alter realized results.
A roll requires separate old realized, roll cash, new obligation, and residual-value records.
Corporate actions, pin risk, after-hours moves, and broker records require final reconciliation.

Common misconceptions

“The name guarantees one fixed four-leg construction.” Direction, ratio, style, and settlement must be verified.
“It is just an iron condor or double calendar.” Its strikes and expirations differ, so the value path is different.
“Front expiration has a fixed maximum gain, profit range, and two breakevens.” Back-option surfaces and executable prices determine conditional results.
“The opening debit is always maximum loss and the later wings automatically handle assignment.” Strike gaps, settlement, stock, funding, costs, and explicit holder action matter.
“Positive Theta or Vega repays the debit, and a roll credit repairs the trade.” Greeks can reverse, while a roll realizes old P/L and opens new risk.