An algebra $$\mathbf{A}$$ is called a perfect extension of its subalgebra $$\mathbf{B}$$ if every congruence has unique to . This terminology was used by Blyth and Varlet [1994]. In the case lattices, this concept described Grätzer Wehrung [1999] saying that congruence-preserving Not many investigations have been carried out so far. The present authors in another recent study faced question whe...