A taxpayer registered under GST must maintain updated contact details to ensure receipt of official notices. The Allahabad High Court ruled that serving notices on registered email addresses constitutes valid service under Section 169 of the CGST Act and Section 13 of the Information Technology Act, 2000, without violating fundamental rights. The court determined that electronic records are deemed received when entering the designated computer system. While taxpayers bear responsibility for maintaining current contact information, tax authorities must ensure reasonable service methods. The decision emphasizes that providing incorrect or inaccessible email addresses may not constitute valid defense, though this depends on individual case facts. - (AI Summary)