This paper compares the policy relevance and derives mathematical relationships between three approaches for GHG emissions accounting for cities. The three approaches are: (a) Purely-Geographic Inventory, (b) Trans-boundary Community-Wide Infrastructure Footprint (CIF), and (c) Consumption-Based Footprint (CBF). Mathematical derivations coupled with case study of three US communities (Denver Colorado, Routt Colorado, and Sarasota Florida), shows that no one method provides a larger or more holistic estimate of GHG emissions associated with communities. A net-producing community (Routt) demonstrates higher CIF GHG emissions relative to the CBF, while a net-consuming community (Sarasota) yields the opposite. Trade-balanced communities (Denver) demonstrate similar numerical estimates of CIF and CBF, as predicted by the mathematical equations. Knowledge of community typology is important in understanding trans-boundary GHG emission contributions.