The concept of Joint Implementation (JI) has been incorporated into the Kyoto Protocol, under both Articles 6 and 12 (the Clean Development Mechanism or CDM). However, a number of outstanding issues remain to be settled: one such issue being the ＇banking of credits earned from JI projects. Currently, the Protocol specifies that ＇donor＇ countries funding JI projects under the CDM may receive credits from 2000 and ＇bank＇ them for use in contributing to their emissions target. Since the emission targets have only been agreed for the period 2008-2012 inclusive, we argue that a:edited CDM action between 2000 and 2008 could be offset by uncontrolled increases elsewhere in the donor country during this time, and hence such crediting could lead to ＇relaxation＇ of the donor country targets. We detail an analysis which attempts to estimate the level of such a relaxation and conclude that it is not negligible. Hence we suggest that CDM credits should be multiplied by a ＇crediting fraction＇, calculated to be between 40% and 70%, to compensate. We then discuss this in respect of the ongoing climate change negotiations, particularly considering the possibility of this sort of banking being introduced for JI projects under Article 6.