The convergence of mobile telecommunications and the Internet global systems forces to reconsider traditional client/server solutions for network and systems management. The paper claims that accounting in the mobility-enabled Internet requires support infrastructures hosted in the fixed network. These infrastructures should monitor, control and register resource consumption locally within the domains where users/terminals dynamically move to, without requiring continuous connectivity with remote and centralized accounting home managers. In addition, the paper shows that the Mobile Agent (MA) technology is suitable to overcome the limits of traditional accounting solutions in several mobility-enabled usage scenarios. MAs can maximize locality in accessing monitoring data, can enable accounting even in case of temporary disconnection, can install new monitoring/control behavior dynamically, and can support session-dependent solutions. The paper finally presents the design and implementation of the MA-based Middleware for Mobility Accounting Management (MAM²), together with some use cases showing the advantages of the MA adoption.