Scrutiny of returns: officer may seek explanations and commence specified enforcement or tax determinations if unresolved. Proper officers may scrutinize filed returns and related particulars, notify discrepancies and seek explanations. If explanations are accepted no further action is taken; if no satisfactory explanation is furnished within thirty days (or extended period), or accepted discrepancies are not corrected in the relevant return, the officer may initiate appropriate enforcement actions or proceed to determine tax and other dues under the assessment provisions.