GST registration amendment must be filed online, validated by the portal, with core-field changes requiring officer approval. Form GST REG-14 requires online submission of an amendment application with GSTIN/UIN, business name, registration type, amendment summary, supporting documents and a signed declaration. The portal validates PAN, Aadhaar, DIN and CIN and issues an ARN; mobile and email changes require online verification. No fee applies. Core fields (business name, principal/additional places, and key personnel details) need Proper Officer approval after verification; non-core amendments do not. A change in constitution causing a PAN change necessitates fresh registration. Authorized signatory must not be a minor.