The "Hidden Foster Care Transparency Act" aims to increase transparency regarding children separated from their parents through arrangements that lack formal court oversight or state responsibility. These "hidden foster care arrangements" include situations where child protective services agencies suggest or insist a child live with someone else due to abuse or neglect allegations, without a court order, or through informal agreements like "kinship diversion" or "safety planning." The bill seeks to shed light on these separations that occur outside the formal foster care system. As a condition for receiving federal foster care funds, states will be required to submit comprehensive data to the Secretary of Health and Human Services. This data must include the number of children separated , how these arrangements ended, the types of allegations involved, and whether parents received legal counsel. States must also report on the length of these arrangements and the specific services provided to families and caregivers. The Secretary will use this state-reported data to produce an annual report to Congress , which will be made publicly available. This report will summarize national trends, including the total number of children in hidden foster care and the outcomes of these arrangements. The Secretary is also tasked with ensuring that data collection is consistent and standardized across states to provide a comprehensive national picture, while avoiding duplication of existing child welfare data.