Understand implied SPX and NDX prices

Enable the estimate deliberately

The optional preference Show implied SPX and NDX prices when closed extends eligible off-cash displays with explicitly modeled index prices. Open Settings → Preferences, enable it and save the form. Return to a supported quote or chart and inspect its implied-price methodology label. During cash hours, official index observations remain official data. Outside cash hours, the model can use observed micro-futures movement with a dated official cash-close anchor. The preference changes which eligible presentation you request; it does not grant missing upstream permissions or guarantee that every off-cash minute is available.

Understand the preferred calculation

For SPX, the preferred estimate uses MES; for NDX, it uses MNQ. Conceptually, the model adds the official index cash close and the observed same-contract micro-futures change since the matched futures cash-close reference. That constant offset is applied to open, high, low and close when forming modeled candles. The futures anchor must belong to the exact dated contract and the same closing boundary as the official index anchor. A contract roll therefore requires a matching new reference rather than borrowing a convenient anchor from another expiry.

Inspect an implied quote or candle

Use the actual displayed explanation to distinguish modeled prices from official observations and to understand the evidence behind a particular point.

1. Save the implied-price preference in Settings → Preferences.
2. Open an eligible SPX or NDX quote or chart outside the relevant cash period.
3. Look for the Implied price on SPX/NDX methodology chip or equivalent implied-price labeling.
4. Hover a modeled candle to inspect OHLC, observation time and the calculation's dated inputs.
5. Compare that index's own source identity and anchor, rather than assuming SPX and NDX share one reference.

Read the modeled day and gaps correctly

The modeled trading-day window runs from 18:00 Eastern Time on the preceding date through 17:00 Eastern Time on the selected trading date. Those display bounds are separate from an actual options session. The existence of the window does not establish that fresh futures observations exist throughout it. Maintenance, weekends and missing source minutes remain gaps. Explicit historical off-cash targets can still be inspected while today's cash market is open. Coarser views preserve gaps and can distinguish buckets containing a mixture of official cash and modeled observations.

Keep modeled prices separate from forecasts and official prints

An implied index estimate approximates price from observed related-market movement. It does not become an official index print, and the constant-basis method does not continuously model financing costs or dividends. Forecast projections are another separate layer with their own model meaning and knowledge cutoff. A forming modeled candle can be partial if it is built from actually captured trades after startup. Completed provider bars can supersede partial captures. Later observations must not appear as if they were already known at an earlier historical read time.

Recognize inputs that the estimate cannot supply

The model does not manufacture index execution count, index trade volume or index VWAP from the futures series. Those index fields remain unavailable when the source does not provide them. SPX can have an explicitly labeled eligible options-parity fallback when a verified micro-futures basis is absent; NDX does not inherit SPX's parity method or anchors. A future-price-coordinate setting is also a different feature: it projects eligible underlying levels onto a futures price scale rather than estimating the off-cash index itself. Read the methodology instead of treating these similarly related displays as interchangeable.

Troubleshoot a missing off-cash estimate

Check that the preference was saved and the tool supports the implied presentation. Verify the selected index, date and actual off-cash time. Missing cash-close anchors, mismatched futures expiries, stale futures or missing observed minutes can correctly prevent an estimate. The source needs current eligible evidence, not merely a visible evening window. If an official bar is flat, do not assume it must be replaced by a model; official observations retain their own provenance. Include the index, selected time, methodology label and dated input explanation when asking support about an unexpected gap or value.