The practical reality
China is the biggest single non-EU exporter of CBAM-scope goods. Large steel and aluminium groups usually have the measurement infrastructure to report real data; smaller forgers and casters may not.
Chinese supplier forms in Mandarin are planned but not live yet — the timing depends on finishing the Mandarin forms and verifier capacity. In the meantime, you can collect data in English through the supplier portal.
What to ask
Same as any CBAM supplier: fuel and electricity use for the installation, tonnes produced by CN code, precursor origin and any existing emissions data.