Starting January 1, 2026, goods imported begin accumulating obligations. CBAM certificates go on sale starting February 1, 2027. The deadline for the first annual declaration and submission of certificates is September 30, 2027, reporting imports for the full year 2026. Some articles online mention "May 31 each year," but that was the old rule before the 2025 amendment.
Complete information and tariff code list: https://patisco.com/zh/eu-check/cbam Search by tariff code to find which new EU regulations apply to you: https://patisco.com/zh/eu-check