This study provides a preliminary simulation-based analysis of how adopting a multi-address system and reflecting living population mobility in grant allocation could reshape local governments’ welfare financing and fiscal responsibility. Under a fixed grant envelope, some high-demand non-metropolitan areas may gain fiscal capacity, while metropolitan commuter cities could face increased pressure. The findings underscore that achieving welfare equity and fiscal accountability in an era of expanding living spaces depends on coherent alignment among population statistics, intergovernmental finance, and welfare delivery systems.