This paper explores a retrospective analysis of children's file data as a research method of gathering information on children's experiences of informal disclosure of child sexual abuse. This study extracted data from files where children were seen for a child sexual abuse evaluation in Ireland and the children were deemed to have given a credible account of abuse by the professionals concerned. A content analysis was conducted using themes identified in previously published research, based on direct interviews with children about their experiences of informal disclosure. The paper discusses the relative merits and limitations of this method, through reporting on the findings of the file analysis and comparing these findings with findings obtained from a smaller sub‐sample of this sample of children, who were interviewed about their experiences of disclosure. It is suggested that this method is worth exploring with a larger sample size which would enable statistical analysis and thus explore the predictive factors influencing early informal disclosure. Frontline services can contribute to the knowledge base on what helps children tell through service‐based research that uses data already collected from evaluation interviews with children, thus eliminating the need to interview children for research purposes. Copyright © 2015 John Wiley & Sons, Ltd. ‘A content analysis was conducted using themes identified in previously published research’ Key Practitioner Messages Frontline professionals gather useful data on a daily basis on informal disclosures of child sexual abuse. Practitioners can contribute to the knowledge base on informal disclosure by systematically gathering information from service users. We need more information on what helps children tell. We therefore need to explore innovative methods of gathering such information directly from children in ways that do not rely on interviewing children repeatedly yet include the child's voice. ‘We need more information on what helps children tell’