Failure to file returns triggers a statutory notice requirement and permits best judgment assessment by the tax officer. The proper officer must first issue a notice under section 32 requiring the taxable person to furnish the return within a specified period, which must be at least fifteen days under section 46. If the person fails to file within that period, the proper officer may assess the tax liability of the return defaulter to the best of his judgement, taking into account all relevant material available, pursuant to section 46.