The article "A generation is all they need" lays out the possible ways that the public could be sold on implantable ID chips/RFID tags that could be used to make purchases and for other purposes. It gets one thing wrong in the intro:

millions of consumer goods are now traced with tiny radio frequency identification chips that allow satellites to reveal their exact location

As far as I know, there are two types of RFID chips: ones that transmit signals and ones that only respond to transmitted signals. The latter are less expensive, the former are probably only used in higher end items, and I don't think either kind can be tracked from space.

Nevertheless, the scenario presented is probably close to how it will be attempted:

...the first widespread use of human implanting will occur in nations at the periphery of the Western world...

...An increasing array of hypothetical chipping scenarios will also be depicted in entertainment media, furthering the familiarization process.

In the West, chips will first be implanted in members of stigmatized groups... Even accused individuals will be tagged, a measure justified on the grounds that it would stop them from fleeing justice... ...welfare recipients will receive their benefits as electronic vouchers stored on their microchips...

...Civil libertarians will try to foster a debate on these developments. Their attempts to prohibit chipping will be handicapped by the inherent difficulty in animating public sympathy for criminals and welfare recipients...

...Mandated to determine the legality of such initiatives, privacy commissioners and Senate Committees will produce a forest of reports presented at an archipelago of international conferences. Hampered by lengthy research and publication timelines, their findings will be delivered long after the widespread adoption of chipping is effectively a fait accompli. The research conclusions on the effectiveness of such technologies will be mixed and open to interpretation.