Scrutiny of returns: officers may seek explanations for discrepancies and proceed to enforcement or tax determination if unresolved. The proper officer may scrutinize a registered person's return and related particulars, notify any discrepancies and seek an explanation; if the explanation is acceptable, no further action is taken. If no satisfactory explanation is furnished within thirty days or any permitted extension, or if accepted discrepancies are not corrected in the return, the officer may initiate enforcement measures or proceed to determine tax and other dues under the statutory assessment provisions, including the newly inserted assessment provision.