Mark, index and last price: which number controls the event?

A derivatives chart can show a trade above a price level while the account's risk calculation uses a value below it. That apparent contradiction may come from comparing different price fields. The last price records an execution. An index estimates a reference market. A mark is the venue's valuation input for specified purposes.

The task is to identify the price that controls each event before asking whether a chart crossed a threshold. A screenshot containing only “BTC price” is incomplete evidence for a derivatives incident.

Three fields, three jobs

Kraken's futures ticker documentation exposes separate fields for last fill, real-time index and mark price. It also identifies the product and includes market bid and ask information. A last fill establishes that a transaction occurred at a price. It does not establish the price at which another quantity can immediately trade, or the valuation assigned to an open position.

An index follows an administrator's construction rules. As an example, the CME CF Bitcoin Real Time Index aggregates order data from qualifying bitcoin-dollar venues. That is different from simply taking the most recent trade on a single derivatives exchange. The relevant source markets, quote currency and aggregation method belong in the definition of the index.

The index is still a calculated reference, not an offer to execute an order. Two indices can measure related markets differently. Reading the name and methodology matters more than assuming that anything labelled “spot” is interchangeable. Our guide to USD and USDT quote assets explains another reason price labels need precision.

The mark is a rule, not an independent trade

Kraken's EEA linear derivatives specifications provide a concrete example: the mark adds a smoothed difference between impact mid price and index price to the index. The perpetual specification describes a premium cap and a fallback when the index is unavailable. The smoothing, cap and fallback are parts of that product's method, not universal properties of crypto derivatives.

This means a mark can differ from both the latest execution and the current index without being a data error. Reconstructing it can require a recent sequence of inputs, rather than one snapshot. The documentation also defines impact mid using prices for a specified contract value, making the calculation more specific than simply averaging the best bid and ask.

Kraken's portfolio-management explanation says its current-price estimate is used for margin management and does not determine the actual profit or loss realised when a position closes or settles. A risk valuation and an exit execution are separate records. The exact liquidation event also depends on the account's equity and requirement, not on a price field in isolation.

An illustrative evidence tuple

Suppose a fictional linear perpetual reports the following at one observation time. All prices are invented dollars per unit; there is no real contract or historical event behind them.

Under those expressly simplified rules, the margin trigger has been reached and the stop's trigger has not. There is no contradiction: each rule reads a different field. The table does not calculate a real liquidation price, reproduce a mark formula or claim that a venue processed these events in this order.

Trigger settings can be configurable. Kraken's derivatives bracket-order guide offers mark, index and last price as conditional trigger signals. That documentation is a reason to retrieve the accepted order settings; it is not a reason to presume which option a customer selected.

Preserve the price type with its clock

For a meaningful reconstruction, retain the venue, exact contract, quote currency, price type, timestamp, and relevant rule version. Add the account's margin state and the order's chosen trigger reference. Then compare the event record with the appropriate time series.

A later chart screenshot cannot substitute for the missing observations, especially if it plots last trades while the disputed event uses a mark. The broader problem resembles stale oracle inputs: a number's source and clock affect what it can prove. The venue and benchmark examples here were checked on 23 September 2026; another product can use another method.

A reported last price can also remain unchanged when no new trade occurs, even as valuation inputs move. Where the data permits, retain the last execution’s own event time alongside the time the feed was observed. A recent download does not make every field a recent execution.