We study behavioural responses to a widely-used tax enforcement policy that combines elements of self- and third-party reporting. Taxpayers self-report to the tax authority but must file
documentation issued by a third-party to corroborate their claims. Exploiting salary-dependent cutoffs governing documentation requirements when claiming deductions for charitable contributions in Cyprus, we estimate that deductions increase by Β£0.7 when taxpayers can claim Β£1 more without documentation. Second, using a reform that retroactively shifted a threshold activating
documentation requirements, we estimate that at least 64% of the response is purely a reporting adjustment. Finally, reporting thresholds affect the responsiveness to tax subsidies
