Section 23.155 - Calculation of variation margin(a)Means of calculation.(1) Each business day each covered swap entity shall calculate variation margin for itself and for each counterparty that is a swap entity or a financial end user using methods, procedures, rules, and inputs that to the maximum extent practicable rely on recently-executed transactions, valuations provided by independent third parties, or other objective criteria.(2) Each covered swap entity shall have in place alternative methods for determining the value of an uncleared swap in the event of the unavailability or other failure of any input required to value a swap.(b)Control mechanisms.(1) Each covered swap entity shall create and maintain documentation setting forth the variation methodology with sufficient specificity to allow the counterparty, the Commission, the registered futures association, and any applicable prudential regulator to calculate a reasonable approximation of the margin requirement independently.(2) Each covered swap entity shall evaluate the reliability of its data sources at least annually, and make adjustments, as appropriate.(3) The Commission or the registered futures association at any time may require a covered swap entity to provide further data or analysis concerning the methodology or a data source, including: (i) An explanation of the manner in which the methodology meets the requirements of this section;(ii) A description of the mechanics of the methodology;(iii) The conceptual basis of the methodology;(iv) The empirical support for the methodology; and(v) The empirical support for the assessment of the data sources.