Processing of returns: summary adjustments determine tax or refund, while notice-triggered inquiry leads to full assessment. Section 143 provides a two-track assessment scheme: summary processing of returns with specified adjustments (arithmetical errors, apparent incorrect claims, late prior-year claim disallowances, audit-identified increases, and additions from information returns), computation of tax, interest and fee on the adjusted total, set-off of credits and reliefs, and issuance of intimation specifying tax payable or refund; alternatively, where the Assessing Officer issues a notice requiring evidence or attendance, a full assessment is made after hearing evidence. Centralised processing and assessment schemes may be prescribed, and special safeguards apply for entities enjoying statutory approvals or exemptions.