I've seen too many buyers trust a PDF certificate without verifying. Here's the actual process:
Step 1: Ask supplier for their UL file number (format: E followed by 6 digits, e.g., E123456). Not the "UL number" on a certificate — the FILE number.
Step 2: Go to https://productiq.ul.com (free account required)
Step 3: Search the file number. Verify:
- Status is "Active" (not "Cancelled" or "Expired")
- Applicant/Listee company name matches the factory name EXACTLY. "Shenzhen MingWei Lighting Co Ltd" ≠ "Shenzhen MingWei Lighting Technology Co Ltd"
- Product category matches what you're buying
- The specific model number appears in the listing
Step 4: If the supplier says "we have ETL instead" — that's fine. Check https://www.intertek.com/directories/ the same way. UL and ETL are equivalent (both NRTL certified to UL 1598/UL 8750).
Red flags:
- Supplier provides certificate but refuses to give file number
- File exists but company name doesn't match (borrowed cert)
- File is active but product category is wrong (cert for LED drivers, selling complete fixtures)
- Certificate date is recent but file was created years ago (bought an old shell company)
This takes 5 minutes and has saved me from 3 bad suppliers.