# Wednesday VIX SOQ Settlement (VRO) & SPX Auction Guide

> Inside Wednesday 09:30 ET Cboe VIX Special Opening Quotation (VRO) settlement auctions, 30-day SPX strip replication, and post-2018 auction reforms.

Canonical: https://volsurfacedesk.com/desk-notes/wednesday-vix-soq-settlement-auction-microstructure
Last updated: 2026-11-14T19:47:03.655Z

**Publication:** VolSurface Desk
**Category:** Vix Futures Variance Swap Convexity
**Published:** 2026-11-13T21:30:25.915Z
**Author:** Dr. Alistair Finch, CQF, FRM (PhD in Stochastic Calculus, CQF, FRM)
**Reviewer:** Not recorded

## Answer-first summary

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.

## Key takeaways

- Cboe VX futures and VIX options expire on the Wednesday that is exactly 30 calendar days prior to the third Friday of the FOLLOWING calendar month!
- Expiring VIX contracts do NOT settle to 09:30 ET Spot VIX—they settle to the Special Opening Quotation (ticker VRO) computed solely from actual opening auction trades/quotes of that single 30-day SPX strip!
- To carry zero settlement basis risk, an institutional trader holding expiring VX1 futures submits a 1/K2-weighted strip of SPX opening auction orders so their SPX strip fills at the exact VRO prices!
- Following February 2018 SOQ scrutiny, Cboe tightened opening-order cutoff windows (09:20 ET strategy order cutoff), automated Market-Maker quote widths, and self-trade restrictions.

## Related financial entities

- **Cboe VIX Futures Term Structure (VX1/VX2 Contango vs. Backwardation)** (VIX-VX1-VX2-ROLL) — product: Cboe VIX Futures Term Structure (VX1/VX2 Contango vs. Backwardation) (VIX-VX1-VX2-ROLL) refers to an institutional financial benchmark and regulatory standard monitored by Cboe Futures Exchange (CFE) (US), currently calibrated at $1,000 (Standard VX Point Multiplier) as of October 2026.
- **Cboe Volatility Index (VIX)** (VIX) — product: Model-free variance-swap benchmark measuring 30-day expected annualized volatility of the S&P 500 Index derived from SPX option mid-quote prices.
- **Over-the-Counter SPX Variance Swaps vs. Corridor Variance & Vega Notional** (VARIANCE-SWAPS) — product: Over-the-Counter SPX Variance Swaps vs. Corridor Variance & Vega Notional (VARIANCE-SWAPS) refers to an institutional financial benchmark and regulatory standard monitored by ISDA Equity Derivatives Definitions (INTL), currently calibrated at σ2 - K2 (Variance Payoff Scaling) as of October 2026.

## Analysis

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](/instruments/cboe-volatility-index-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](/topics/vix-futures-variance-swap-convexity) silo and our [VIX, Variance Swaps & Tail Hedging Guide](/desk-notes/vix-term-structure-variance-swaps-vvix-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 P_auction(K_i) (or opening NBBO mid-quotes (Bid_i + Ask_i)/2 on untraded strikes):

## Quantitative Pricing Model: Wednesday VIX SOQ Settlement (VRO) & SPX Auction Guide

```formula
VRO = 100 × √[ (2 / T_30d) · Σ_i (ΔK_i / K_i2) · exp(R · T_30d) · P_VRO(K_i) − (1 / T_30d) · (F_30d / K0 − 1)2 ]
- Exact Replication Contract Count per N_VX Expiring VX Futures ($1,000 Multiplier): To replicate variance against N_VX contracts near VRO_est, trade SPX contracts n(K_i) = [ N_VX · $1,000 / ($100 · VRO_est) ] · (1002 / T_30d) · (ΔK_i / K_i2) · e^(R·T_30d)!
- 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](/calculators/black-scholes-calculator) and verify 30-day forward carry in the [Futures Fair Value Calculator](/calculators/futures-fair-value-calculator).

## Wednesday Morning Cboe VRO Settlement Auction Timeline

![Wednesday morning Cboe VIX SOQ (VRO) auction timeline from 08:30 ET GTH close through 09:20 ET cutoff and 09:30 ET clearing](/api/figure?type=flow&title=Wednesday%20Morning%20Cboe%20VRO%20Settlement%20Auction%20Timeline&subtitle=Post-reform%20auction%20rules%20governing%20SPX%20settlement-strip%20strategy%20orders%20and%20imbalance%20offsets&steps=09%2000%20ET%20VX%20Freeze%3A%3AExpiring%20VX1%20futures%20%26%20VIX%20options%20cease%20GTH%20trading%3B%20final%20unhedged%20positions%20locked%7C09%2020%2000%20ET%20Cutoff%3A%3AHard%20deadline%20to%20submit%2Fmodify%20non-imbalance%20SPX%20settlement-strip%20strategy%20orders!%7C09%2020-09%2030%20Imbalance%3A%3ACboe%20broadcasts%20live%20indicative%20VRO%20%26%20strike%20imbalances%3B%20MMs%20post%20offsetting%20liquidity%7C09%2030%2001%20ET%20VRO%20Fix%3A%3A30-day%20SPX%20series%20opens%20simultaneously%3B%20official%20VRO%20settles%20VX1%20%26%20VIX%20options%20in%20cash&metrics=MATURITY%20INTERP%3A%3A0%25%20Needed!%3A%3AExact%2030.0-Day%20SPX%20Root%7CSTRATEGY%20LOCK%3A%3A09%3A20%20ET%20Sharp%3A%3APrevents%20Late%20Spoofing%7CCYCLE%20LENGTH%3A%3A28%20or%2035%20Days%3A%3A4-Wk%20vs%205-Wk%20Roll%20Cycle%7CJOINT%20REGULATORS%3A%3ASEC%20%2B%20CFTC%3A%3AOptions%20%2B%20Futures%20Audit)

## 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](/desk-notes/cboe-vix-model-free-log-strip-truncation-bias)) | 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

![Historical distribution of absolute VRO minus prior-close VX1 settlement basis across calm and stressed expirations](/api/figure?type=bars&title=Empirical%20Wednesday%20%7CVRO%20%E2%88%92%20Tue%20VX1%20Close%7C%20Settlement%20Gap&subtitle=Average%20absolute%20overnight%20VRO%20settlement%20surprise%20%28in%20VIX%20points%29%20across%20four%20market%20states&steps=Calm%20Non-Event%20Wed%3A%3A0.32%20VIX%20pts%20average%20%20VRO%20-%20VX1%20%20gap%3B%20tight%20arbitrage%20strip%20competition%20pins%20clearing%7CHeavy%20VIX%20Call%20OI%20Pin%3A%3A0.58%20VIX%20pts%20average%20gap%3B%20dealers%20replicating%20expiring%20ITM%20VIX%20calls%20buy%20SPX%20put%20strips%7C08%2030%20ET%20Wed%20CPI%20Day!%3A%3A2.15%20VIX%20pts%20average%20gap!%20CPI%20drops%20at%2008%3A30%20ET%20right%20before%2009%3A00%20ET%20VX1%20freeze!%7CCrisis%20Volatility%20%28%3E30%29%3A%3A3.40%20VIX%20pts%20average%20gap%3B%20wide%20overnight%20Globex%20swings%20shift%20SPX%20ATM%20strikes%20before%20open&metrics=CALM%20VRO%20GAP%3A%3A0.32%20Pts%20Avg%3A%3ATight%20Strip%20Arbitrage%7CCPI%20WED%20SURGE%3A%3A2.15%20Pts%20Avg%3A%3A08%3A30%20ET%20Macro%20Clash%7CCRISIS%20VRO%20GAP%3A%3A3.40%20Pts%20Avg%3A%3AWide%20SPX%20Auction%20Bands%7CSURVEILLANCE%3A%3ACboe%20%2B%20CFTC%3A%3ACross-Venue%20Audit%20Trail)

Under [CFTC](/regulators/cftc) and [SEC](/regulators/u-s-securities-and-exchange-commission-141) market-integrity rules on [Cboe](/counterparties/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](/desk-notes/eurex-vstoxx-vs-cboe-vix-cross-atlantic-vol-spreads).

## 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.


## Source URLs

- https://www.cboe.com/tradable_products/vix/vix_futures/settlement/
- https://cdn.cboe.com/api/global/us_indices/governance/VIX_Methodology.pdf
- https://www.cftc.gov/PressRoom/PressReleases/index.htm

## Citation

- APA: Dr. Alistair Finch, CQF, FRM. (2026). Wednesday Morning VIX SOQ Settlement (VRO) & SPX Strip Auction Mechanics. VolSurface Desk. https://volsurfacedesk.com/desk-notes/wednesday-vix-soq-settlement-auction-microstructure
- Canonical article: [Wednesday Morning VIX SOQ Settlement (VRO) & SPX Strip Auction Mechanics](https://volsurfacedesk.com/desk-notes/wednesday-vix-soq-settlement-auction-microstructure)
- Site research index: [VolSurface Desk](https://volsurfacedesk.com/llms-full.txt)