GDPR protects natural persons and self-employed individuals (sole traders).
This means that the protection of personal data also applies to individuals with a business registration number (IČO).
Personal data relates to living natural persons — GDPR explicitly excludes from its scope
data concerning deceased individuals.
A data subject cannot be a legal entity. This means that companies are not covered by this protection (i.e., there is no requirement to have a legal basis for processing such data, as it is not considered personal data).