The best way to determine if an advertiser has a prefix is to contact customer service. They can provide prefix information and next steps on how to gain access.
You can also use the Prefix Search feature when logged in to the Ad-ID system.
1. Go to the Search menu in the top navigation bar and select Prefix Search.
2. Search by prefix or company name. Enter a 4-character prefix or company name. Click Submit.
3. If a prefix is found, the results will be displayed.