Social Policy & Administration published by John Wiley & Sons Ltd.In this paper, we examine the discretionary uses of documentation in the implementation of naturalisation through a comparative perspective focusing on Belgium, France and the United Kingdom. We investigate the organisational and professional factors that are likely to impact variation in the uses of discretion based on documentation. Belgium, France and the United Kingdom represent three interesting case studies involving different actors with different mandates. In Belgium, municipal agents are responsible for a mandatory check of applicants documents before transferring the naturalisation application to public prosecutors. While only the latter have the mandate to check that the legal requirements are met, most municipal agents are involved in the examination of the requirements. In France, before the digitisation of nationality acquisition in 2023, the initial acceptance of an application involved prefectural agents who had the power to refuse application registration if the documentation was deemed insufficient or u2018non-compliantu2019. In the United Kingdom, u2018Nationality Checking Servicesu2019 (NCS) were available until 2019 in local register offices for an optional check of the application before the transfer to the Home Office, which remains the decision-making body on nationality applications. As United Kingdom law regulates strictly immigration advice, NCSs were often unwilling to express themselves on the chances of an application. Drawing on ethnographic fieldwork consisting of interviews with implementation agents in the three countries and observations of their interactions with applicants, this paper contributes to shedding light on what drives variations in the governance of access to nationality through paperwork.