An Ockham algebra L=(L,∧,∨,f,0,1) that satisfies the identity f2n+m=fm, n∈N and m∈N0, is called a Kn,m-algebra. In this paper we describe the complement (when it exists) of a principal congruence and characterize these congruences that are complemented.Fundação para a Ciência e a Tecnologia (FCT) - programa POCT