There are many methods for estimating size, effort, schedule and other cost aspects of IS projects, but only one specifically developed for Enterprise Resource Planning (ERP) (Stensrud, Info Soft Technol 43(7):413–423, 2001) and none for simultaneous, interdependent ERP projects in a cross-organizational context. The objective of this paper is to sketch the problem domain of cross-organizational ERP cost estimation, to survey available solutions, and to propose a research program to improve those solutions. In it, we: (i) explain why knowledge in the cost estimation of cross-organizational ERP is fragmented, (ii) assess the need to integrate research perspectives, and (iii) propose research directions that an integrated view of estimating cross-organizational ERP project cost should include.