Index Linked Contract can be used by National Grid ESO to meet the [voltage requirement](https://www.nationalgrideso.com/transmission-constraint-management?market-information "voltage"). The contract is normally enacted in the morning ahead of the power exchange auction. The generator will get paid based on the agreed strike price. The generator will also be compensated if the generation spread is negative, if positive, the positive spread will be deducted from the strike price. As the generation spread is calculated based on the outturn market indices, so the name of index linked contract.