Tax withholding return filing obligations: electronic submission mandated with defect rectification leading to invalidation if not cured. Section 206 requires designated persons who deduct tax at source to prepare and deliver prescribed returns after each financial year to the prescribed authority; the Board may frame a scheme for alternative filing. From 1 April 2005 returns may be delivered on computer readable media as per a Board-specified scheme, and such electronic returns are admissible as evidence. If an electronic return is found defective, the Assessing Officer must notify the deductor and allow 15 days (or a further permitted period) to rectify; non-rectification renders the return invalid and treated as non-delivery.