Following some of the directives and regulations in the 3rd EU Energy Package, many of the EU members are reconsidering their methodologies to derive the tariffs charged for access and usage of their gas transport systems. Among these methodologies, the use of entry-exit tariffs computed via least squares has received the most attention over the last few years and there is a wide consensus towards the application of this approach. The main contribution of this paper is to raise awareness on the fact that, even after a given methodology has been chosen, there are still important details to be fixed before the final tariffs are computed. Within the context of the least squares methodology we argue that, although many of these details may seem minor, they can have a big impact on the final outcome. The paper also presents proposals on how these details can be handled while still pursuing the goals set by the EU; goals such as being transparent, cost-reflective, and non-discriminatory. Finally, the paper concludes with an illustration of the discussed proposals, applying them to the Spanish gas transport network. (C) 2013 Elsevier Ltd. All rights reserved.