To ensure a majority of emission reductions required under the program occur at covered entities and facilities, the WCI Partner jurisdictions set a limit on the use of offset credits issued by the WCI, as well as offsets and allowances issued by other trading systems that are recognized by the WCI Partner jurisdictions, to no more than 49 percent of the total emission reductions from 2012 to 2020. This limit and rationale are established in the WCI's Design Recommendations.

To develop the recommendations for implementing the WCI offset limit, the WCI Cap Setting and Allowance Distribution (CSAD) Committee produced a background paper and solicited and carefully considered stakeholder comments. In May 2009, CSAD issued a white paper and hosted a stakeholder workshop. On the basis of input received and further deliberations, CSAD developed draft recommendations on how to implement the offset limit, which were posted for stakeholder comment in October 2009. The WCI Partners considered these comments, further discussed the recommendations at their March 3 meeting in Vancouver, and have since approved the recommendations. The document describing the recommendations for implementing the offset limit is available at westernclimateinitiative.org.