Every genuine company leaves a paper trail. In the UK, Companies House provides free access to incorporation documents, officers, and accounts. In the US, Secretary of State websites offer equivalent business-entity searches. If a name produces no result in any registry, treat claims made under that name with caution.
For financial businesses, go further: investment advisers appear in the SEC's IAPD database, brokers in FINRA's BrokerCheck, and UK firms in the FCA register. Cross-check the domain itself through WHOIS/RDAP records and the web archive. When a company's only trace is its own website, that absence is itself a finding.