What is a DNC list?
A DNC (Do Not Call) list is a list of phone numbers that must not receive telemarketing calls. The best known is the FTC's National Do Not Call Registry; every telemarketer must also keep its own internal list of people who asked it to stop calling.
Under the FCC and FTC rules, sellers must check their call lists against the national registry at least every 31 days and drop registered numbers, unless they have the person's written permission or an established business relationship. Internal opt-out requests must be honored within a reasonable time, no more than ten business days. Several states also run their own registries with their own rules.
The registry covers consumer numbers, so most purely business-to-business calls fall outside it, but internal Do Not Call requests apply either way. For the mechanics of scrubbing a calling list, see how to scrub DNC lists for AI outbound campaigns.