Most research on the social policy–migration control link focuses on indirect control, that is, denying access to welfare. This article instead draws attention to how welfare institutions are made directly involved in migration control through duties to report certain categories of migrants to migration authorities. We ask how these obligations are put into practice and how local governments shape this process. In so doing, we place special emphasis on local organisational fields – that is, the close horizontal connection between public and non-public actors involved in basic needs provision. The article builds on exploratory research across four German cities, drawing on 61 interviews conducted in 2019–2020 with welfare actors catering to basic needs (housing/shelter, healthcare, social assistance, social counselling) and document research. Based on this, we, first, explore patterns of reporting practices and provide a typology of different responses, ranging from elaborate circumvention strategies to over-compliance. Second, we analyse the domino effects of reporting obligations, namely how welfare actors that are exempted from reporting adopt their practices too, with consequences both for migrants' welfare access and for other authorities' ability to report. Finally, we discuss how local governments can shape reporting practices, demonstrating how some cities actively sanction circumvention strategies. The last part identifies venues for further research.