AbstractThe UK social security system performs an important role as a creditor and debt collector for many benefit claimants, with more affected by deductions than formal welfare conditionality or sanctions. Deductions, then, are central to understanding low‐income life in the UK. With that in mind, this paper draws on a mixed‐methods project to explore the policy rationale, administration and effects of benefit deductions at a particular moment of crisis. Through new analysis of statistical releases, I evidence increasing indebtedness and an Inverse Care Law, whereby UK social security performs worst for those who need it most. Drawing on qualitative longitudinal ethnographic fieldwork conducted at the height of the cost‐of‐living crisis, I also evidence how deductions affect the lives and trajectories of low‐income claimants over time. The analysis offered details how deductions weaponize debt, often in ways that financialise benefit claimants and their entitlements that prove counter‐productive to the stated policy objectives of deductions: worsening the poverty‐debt trap and pushing people (further) away from the labour market.