Resolve the PSC ownership chain for a company, traversing corporate entity PSCs recursively.

Starting from the given company, fetches its PSCs. When a PSC is a corporate entity registered at Companies House, follows it to find that company's PSCs, and so on, until reaching natural persons, foreign entities, or the depth limit.

Terminal reasons explain why a branch stopped:

• natural_person - reached an individual (ultimate beneficial owner)
• legal_person - reached a legal person (e.g., government body)
• super_secure - person's details protected by court order
• foreign_entity - corporate entity with no registration number filed at all
• unverified_registry - a registration number is filed, but it cannot be tied to the Companies House register (a foreign registry, or a registry name we do not recognise). The branch stops rather than following a number that may belong to an unrelated UK company. registry_number and registry_name on the node say what was filed.
• depth_limit - max traversal depth reached
• not_found - company not found or API error
• cycle_detected - circular ownership detected
• psc_exempt - company exempt from PSC filing (e.g., listed PLC)
• unknown_kind - Companies House returned a PSC kind we have not classified. The branch stops rather than guessing; kind_raw carries the raw value.

ECCTA identity verification. Every individual node in the tree - at any depth, including the ultimate beneficial owners the chain exists to find - carries the same four fields as /company/{number}/psc, with the same meanings:

• verification_status - verified | pending | overdue | unknown
• identity_verified - true (verified), false (overdue only), or null for pending and unknown. A pending person has missed nothing.
• identity_verified_on - set only when verification_status is verified
• verification_deadline - that person's own Companies House deadline, set only when pending or overdue. Companies House's open-ended-window sentinel (9999-12-31) is never surfaced; such a person is pending with a null deadline.

Corporate-entity, legal-person, super-secure and unknown nodes omit these fields entirely - a company has no personal identity to verify, so a status on one would imply an obligation that does not exist.

Before 2026-08-17 the chain reported no verification data at all, so the same person could appear verified on /psc and blank here (CH-Api#104). Every person in the tree is classified against a single date fixed at the start of the traversal.

Credits: Each company resolved in the chain costs 1 upstream API call. The chain_metadata.total_credits field shows the total cost.

Example: /v1/company/12345678/psc/chain?max_depth=3

{
  "cache_age_seconds": 3421,
  "cached": true,
  "credits_remaining": 487,
  "credits_used": 1,
  "data": {
    "company_age_years": 78,
    "company_name": "TESCO PLC",
    "company_number": "00445790",
    "company_status": "active",
    "company_type": "plc"
  },
  "data_source": "cached",
  "status": "success"
}