“Precursor products” refer to input materials used during manufacturing.
Examples:
For pig iron: the precursor is sintered ore
For crude steel: the precursor is pig iron
For finished steel products: the precursor may be pig iron or crude steel

Yes. During the transition phase, indirect emissions, especially electricity-related emissions for steel, aluminum, and downstream products, must be reported, even if not subject to certificate pricing.

Simple products: Use a ratio of attributable emissions to product output (i.e. emissions intensity)
Complex products: Calculate internal emissions, then add precursor product emissions based on their emission intensity

Companies must monitor, record, and calculate emissions based on output and energy use.
If you're a trader or intermediary, you must collect emission data from manufacturers because you cannot submit CBAM-compliant measured values without actual data.

Yes. CBAM reporting is quarterly. Reports must be submitted within one month after each quarter ends, with modifications allowed within two months.
Starting from 2026, the reporting schedule is as follows:
Q1 Report: Submit by April 30, 2026; modify by May 31, 2026
Q2 Report: Submit by July 31, 2026; modify by August 31, 2026
Q3 Report: Submit by October 31, 2026; modify by November 30, 2026
Q4 Report: Submit by January 31, 2027; modify by February 28, 2027