Enquiry before assessment under section 142(1) covers return filing, books production, and disclosure of assets and liabilities. Enquiry before assessment under section 142(1) allows the Assessing Officer to require a return of income, production of books of account and documents, and information including assets and liabilities. Prior approval of the Joint Commissioner is needed for statements of assets and liabilities not included in the books. Notice under section 142(1)(ii) may be issued whether or not a return has been filed, but only after the section 139(1) time limit has expired.