We examine how administrative design and firms’ reporting infrastructure shape realised access to the UK R&D tax credit. We exploit a sequence of reforms that expanded disclosure requirements and increased administrative scrutiny while leaving statutory eligibility for most SMEs largely unchanged. We frame claiming as a two-stage process in which firms engage when expected benefits exceed fixed reporting costs, and receipt depends on meeting administrative and verification requirements. Using longitudinal UK SME survey data and a difference-in-differences design, we compare firms with and without pre-reform access to professional tax planning advice, treated as a predetermined proxy for reporting capacity. Following the administrative tightening, firms with baseline advisory access show larger increases in both engagement with, and receipt of, R&D tax relief, with effects concentrated on the extensive margin. Event-study analyses show no evidence of differential pre-trends, and placebo tests support a causal interpretation. The findings highlight how reporting requirements and verification intensity, as features of administrative design, shape realised access to tax incentives beyond statutory eligibility, reallocating access toward firms with greater reporting capacity when scrutiny increases.