Vix Futures Variance Swap Convexity
Wednesday Morning VIX SOQ Settlement (VRO) & SPX Strip Auction Mechanics
Examine Wednesday morning Cboe VIX futures and options settlement (ticker VRO): exact 30-day SPX opening auction replication, clearing-price determination, and how dealers convert expiring VX positions into SPX option strips.
Every monthly and weekly Wednesday morning at 09:30:00 ET, billions of dollars in expiring Cboe Futures Exchange (CFE) VX futures and Cboe VIX options cease trading (last trade Tuesday 16:00/16:15 ET or Wednesday 09:00 ET GTH) and cash-settle to a special symbol: VRO (the VIX Special Opening Quotation). Traders who assume expiring VX1 converges to Wednesday's 09:30 ET Spot Cboe VIX screen print routinely get surprised by 0.50 to 2.00 point settlement divergences!
Within the VIX Term Structure, Variance Swaps, Vol-of-Vol VVIX & Tail Hedging silo and our VIX, Variance Swaps & Tail Hedging Guide, mastering the exact 09:20–09:30 ET SPX opening auction microstructure turns settlement risk into clean basis arbitrage.
Exact VRO Pricing Equation and Replication Strip Sizing#
Why is VIX expiration always scheduled on a Wednesday (unless Wednesday is an exchange holiday)? Because counting backward exactly 30.0 calendar days (T_VRO = 43,200 / 525,600 years) from next month's third-Friday 09:30 ET AM-settled SPX expiration lands on Wednesday at 09:30 ET! Consequently, unlike continuous Spot VIX—which must interpolate between two weekly SPXW series—VRO requires ZERO maturity interpolation: it evaluates a single standard SPX expiration using opening auction trade prices Pauction(Ki) (or opening NBBO mid-quotes (Bidi + Aski)/2 on untraded strikes):
Quantitative Pricing Model: Wednesday VIX SOQ Settlement (VRO) & SPX Auction Guide#
- Exact Replication Contract Count per NVX Expiring VX Futures ($1,000 Multiplier): To replicate variance against NVX contracts near VROest, trade SPX contracts n(Ki) = [ NVX · $1,000 / ($100 · VROest) ] · (1002 / T30d) · (ΔKi / Ki2) · e^(R·T30d)!
- Worked Basis Convergence Trade (Tue Close: VX1 = 15.80, Fair 30d SPX Strip = 16.25 [+0.45v Arbitrage Spread], Trade Size = +200 Long VX1):
- Arbitrageur buys +200 VX1 @ 15.80 and submits 09:20 ET Strategy Strip to SELL 1/K2 SPX OTM puts & calls. At 09:30 ET Wednesday, strip auction clears at VRO = 16.42 => Long VX1 gains +$124,000 while short SPX strip locks +16.25 → 16.42 offset, netting +0.45 × $200k = +$90,000 riskless basis!
Traders inspect individual SPX option strip legs in our Black-Scholes Option Calculator and verify 30-day forward carry in the Futures Fair Value Calculator.
Wednesday Morning Cboe VRO Settlement Auction Timeline#
Comparing Spot VIX vs Wednesday VRO Settlement Across Four Dimensions#
| Settlement Feature | Real-Time Spot Cboe VIX (VIX) | Wednesday SOQ Settlement (VRO) | Operational Desk Consequence |
|---|---|---|---|
| Underlying SPX Series | Interpolates 2 SPXW Friday expiries (23–37d) | Single exact 30-day AM SPX root | VRO avoids weekly event weight distortion in Near leg |
| Strike Price Input | 100% electronic NBBO mid-quotes | Actual Opening Trades (mid-quote only if 0 vol) | Heavy auction buy imbalances lift VRO toward SPX ask! |
| Zero-Bid Cutoff Rule | Live two-consecutive $0.00 bid rule (truncation note) | Opening auction clearing + MM width obligations | Cleaner wing inclusion under Cboe auction rules |
| Pinning Effect on VIX | None directly | Heavy expiring VIX option strike OI (e.g., 15, 18, 20) | Expiring VIX option hedges pull VX1 toward big strikes on Tue! |
Empirical Wednesday |VRO − Tue VX1 Close| Settlement Gap#
Under CFTC and SEC market-integrity rules on Cboe, any desk trading expiring VIX options never holds accidental pin exposure past Tuesday 16:00 ET unless actively participating in the 09:20 ET SPX strip replication auction. Compare live parameters in Eurex VSTOXX (FVS) vs Cboe VIX (VX) Spread Trading Guide.
Frequently asked questions
Why are VIX expirations sometimes 28 days apart and other times 35 days apart?
Because VIX settlement is anchored backward—exactly 30 calendar days before the FOLLOWING month’s third-Friday AM SPX expiration! Depending on whether the calendar month has four or five Fridays between third Fridays, the VIX futures cycle spans either 4 weeks (28 days) or 5 weeks (35 days).
Why does Wednesday’s VRO settlement print often differ by 0.40 to 1.80 points from 09:30 ET Spot VIX?
Two reasons: (1) Spot VIX at 09:30 ET blends TWO SPXW expirations (23d and 30d/37d) using electronic mid-quotes, whereas VRO uses ONLY the single exact 30-day SPX series! (2) VRO uses actual opening auction clearing trades where existed (and mid-quotes only on untraded strikes).
How do arbitrageurs convert expiring VIX futures into 30-day SPX variance at 09:20 ET Wednesday?
Suppose VX1 trades 0.35 vol points cheaper than the 30-day SPX option strip on Tuesday afternoon. Arbitrageurs BUY expiring VX1 futures and submit Sell-to-Open SPX OTM put/call strip strategy orders before 09:20 ET Wednesday—locking exact VRO convergence regardless of where VRO clears!
What reforms did Cboe introduce to protect the Wednesday VIX SOQ auction from manipulation?
Cboe instituted an early 09:20 ET cutoff for new/cancelled VIX settlement strategy orders (allowing only imbalance-offsetting orders until 09:30 ET), disseminated real-time indicative VRO auction imbalances every few seconds, and enforced strict non-zero bid/ask width caps.
Publication record
- Published
- November 13, 2026
- Updated
- November 14, 2026
- Author
- Dr. Alistair Finch, CQF, FRM
- Review
- Review not recorded
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- Passed in the stored pipeline record
- Source URLs
- 3 recorded
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Dr. Alistair Finch, CQF, FRM. (2026, November 14). Wednesday Morning VIX SOQ Settlement (VRO) & SPX Strip Auction Mechanics. VolSurface Desk. https://volsurfacedesk.com/desk-notes/wednesday-vix-soq-settlement-auction-microstructureRelated Vix Futures Variance Swap Convexity & Institutional Briefings
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