To ascertain the reasons for and impacts of closed books in general practices in Aotearoa New Zealand and report recommendations for mitigation. A mixed-methods approach was used. A first round of interviews with experts in the primary care sector was conducted, followed by a survey across general practices and, finally, a second round of interviews. Data reported here are qualitative data from the interviews and open-ended questions in the survey. Qualitative data were analysed using a general inductive approach. The key reasons for not enrolling new patients included workforce shortages, high workloads and staff burnout, funding issues, concerns about quality of care and insufficient physical space. These were exacerbated during the COVID-19 pandemic. The impacts included no access or delayed access to primary care, worsening health conditions, undiagnosed or untreated diseases and less or no access to preventive care. Recommendations included recruiting more staff including administrative staff, resolving the pay disparity between general practice and hospital staff, having a longer placement period for students in general practice, utilising a multidisciplinary workforce and revising the funding formula. There is an urgent need to resolve key issues so that general practices can accept all who wish to enrol.