Power to requisition custody material authorises tax officers to obtain material held under other laws for tax proceedings. The Competent Investigating Authority may authorise an income-tax authority (the Requisitioning Officer) to require delivery of material taken into custody under other laws when the material is relevant to tax proceedings, where there is reason to believe a summoned person has omitted or will omit to produce it or the material represents undisclosed tax base or property; the holding officer must deliver the material immediately or when no longer necessary to retain it, and the procedural provisions of section 135 apply.