The High Court held that the Assessing Officer is strictly bound by the limitation prescribed in section 144C(13) for passing the final assessment order after issuance of the draft assessment order and receipt of DRP directions. The chronology of events in the present cases established that the assessment orders were issued beyond the statutory time limit. The court held that when the language of the provision is clear, no external aid of interpretation is required; the amendment to section 144C must be construed in light of the legislative intention to streamline and expedite the DRP mechanism. Once the amended provision became part of the statute, it had to be given full effect, even if section 144C is a machinery provision. Any assessment order passed in violation of the mandatory timeline is invalid. Accordingly, all assessment orders passed beyond the limitation period were quashed.