Why perps do not expire
A perpetual future keeps exposure open without a settlement date. Because there is no final convergence point, venues use funding and mark-price rules to encourage the contract toward a spot-based index. Funding is generally exchanged between longs and shorts; the venue’s exact formula controls who pays, when, and how much.
The displayed annualized rate is a projection, not a promised return. Normalize the interval and model several funding paths before treating carry as an edge.
Index, mark, and last price
The index is usually derived from selected spot markets. The mark price is a risk-management estimate used for unrealized profit and loss or liquidation. The last price is the most recent contract trade. These values can diverge during volatile or thin conditions.
Stops and liquidations may reference different prices. A position plan should show all three and leave enough distance for the exit order to execute before the liquidation engine takes control.
Margin modes and collateral
Isolated margin limits the collateral allocated to a position. Cross margin shares collateral across positions and can create portfolio contagion. Stablecoin, token, and staked-asset collateral each create different sensitivities.
For a deeper treatment, read the research note on perpetual funding rates and the guide to 50x and 100x liquidation math.