Refund time limit extended for CGST claims; return due date clarified for zero-rated SEZ supplies and textual proviso changes. Amendments modify section 54 by substituting wording in sub-section (1)'s proviso, extending the refund claim period in sub-section (2), omitting a cross-reference in sub-section (10), and inserting an Explanation that for zero-rated supplies to Special Economic Zone developers or units where refund of tax paid is available, the due date for furnishing the return in respect of such supplies is the due date for furnishing the return under the return-filing provision.