In this note we present an analogue of equivariant formality in K-theory and show that it is equivalent to equivariant formality á la Goresky-Kottwitz-MacPherson. We also apply this analogue to give alternative proofs of equivariant formality of conjugation action on compact Lie groups, left translation action on generalized flag manifolds, and compact Lie group actions with maximal rank isotropy subgroups.

We would like to gratefully acknowledge the anonymous referee for the critical comments on the early drafts of this paper and especially the suggestions for improving Section 3.3. We would like to thank Ian Agol for answering a question related to the proof of Theorem 3.2.