SDG Target 16.9 neither defines ‘legal identity’ nor proposes any indicator to measure progress other than the coverage of birth registration among those under five years old. Submissions around the indicators focused on the age setting the limit at which coverage of birth registration should be measured (Metadata for Goal 16, 2016). The indicator adopted leaves significant uncertainty on what it would take to know that the target had been reached, especially in its broader definition beyond birth registration (van der Straaten, 2015). The problem of definition starts from the distinction that can be made between identity and identification. An identity is conventionally what a person (or thing) is, in and of itself; a legal identity is the recognition of that identity in law; and identification is the process of establishing that identity and distinguishing the person (or thing) identified from others; which may then be recorded in a register and confirmed by the issuance of a credential of some form – such as an identity document – as proof of the registration. The confusion has led even commercial operators in this space to propose a ‘style guide’ for the use of terminology (Donner, 2018). A person’s ‘legal identity’, an identity they have in law, should be separated from the question of whether they have been formally identified and registered by state authorities and issued a document confirming that registration. Moreover, a person may have multiple legal statuses – or ‘identities’ – in relation to the state, with corresponding entries in official registers and different rights and obligations according to context: as a pensioner, a school-age child, a single or married person, a recipient of state benefits, a voter, an adult due to perform military service, an owner of property, etc. (Brewer et al., 2015). There is no particular requirement that each register be linked within a single national system, and in many states they are not, even as there are procedures to check that multiple registrations can be traced back to a single person. National legal frameworks and institutions for civil registration vary widely: not just between the civil and common law traditions, but with distinctive characteristics in Islamic societies, (formerly) communist states, states that have sought to formalise recognition of customary law, or those where registration is rather at the family or household level. The legal identity field is vastly complicated by these variations, especially as they relate to the recognition of documents issued by foreign governments. As more and more children are born and become adults in a country where neither parent is recognised as a citizen (both in law and in fact), the preservation of the different aspects of their ‘identity, including nationality, name and family relations as recognized by law’ (CRC, Article 8), becomes ever more fragile. These challenges are greatest for refugees and irregular migrants, but have proved difficult to resolve even within the European Union, with the presumption of legal residence that follows from citizenship of another member state (Manby, 2020). The SDG Target did not attempt to address any of these complexities. Instead, the content of the commitment was left vague, beyond birth registration alone. Different actors have chosen to interpret it in light of their own priorities. Legal identity and digital identity The rapid advance of digital technology has created a surge in discussion of the concept of ‘digital identity’ disconnected from the traditional concepts of civil registration. The digital identity possibilities range from the conceptually straightforward digitalisation of paper records; via the addition of biometric identifiers to these registers; to the concept of ‘selfsovereign’ or ‘self-managed’ identity free from reliance on a government database; or the 5