> ## Documentation Index
> Fetch the complete documentation index at: https://docs.numofx.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Mark price and bounds

> Where the futures mark comes from, the limits on how it moves, and what it drives

The mark price is the price the MarginEngine values a futures position at. It drives
[variation margin](/futures#variation-margin), [margin](/risk/margin-math) and
[liquidation](/risk/liquidation). Spot has no mark.

## Where it comes from

Each update, the venue computes a forward from the series' order book, or from the index when the
book is too thin. See [Impact pricing](/markets/impact-pricing). It signs the forward into the
forward feed, and the mark is pulled on chain from that feed. Anyone can trigger the pull.

## Bounds

The chain enforces three limits on every mark update:

| Limit | Value | Getter on `FutureAsset` |
| - | - | - |
| Frequency | At most once an hour | `minMarkInterval()` |
| Move per update | At most 5% from the previous mark | `maxMarkDeviation()` |
| Distance from the index | Inside the index band | `markIndexBand(expiry)` |

The index band is 10% either side of the [index](/markets/index-price). Over the last 14 days before
expiry it narrows linearly to 1%. The same band bounds every fill. See
[The fill band](/futures#the-fill-band).

If the book's price falls outside these limits, the mark moves as far toward it as they allow. If
no mark can satisfy them, or the index is stale, the mark does not update.

## Read it

[`GET /v1/markets`](/api-reference/endpoint/get) reports `mark_price`, `index_price` and
`band_width` for each series. [`GET /v1/positions`](/api-reference/endpoint/positions) reports
`mark_price` and `mark_updated_at` on each position. The mark is quoted in cNGN per USDC.

## At expiry

The mark stops updating at `last_trade_time`. Positions close out at the settlement price, not the
mark. See [Settlement](/futures#settlement).


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