Assessment procedure permits assessment from tax returns with later verification, objection and fresh assessment where material incorrectness exists. The provision creates a two-stage assessment process: an initial assessment from the filed return and accompanying documents without the assessee's presence, allowing adjustments for arithmetic errors, prima facie admissible or inadmissible deductions, and carrying forward earlier computed allowances or losses; followed, where the assessee objects or the officer seeks verification, by a notice for attendance or evidence (subject to supervisory approval in specified cases) and thereafter a written fresh assessment if the prior assessment is found materially incorrect, with safeguards against default treatment and interest on disputed amounts.