For accountancy practices · corporate KYB
KYB onboarding via Companies House for accountants
KYB onboarding wants the full corporate picture: company status + officers + PSC tree + charges + insolvency events + the layered ownership structure that surfaces beneficial owners. The Companies House API gives you each one as a separate request; the layered corporate structure (ParentCo → HoldCo → OpCo → individual UBO) takes 4-5 hops to walk. Doing it correctly is hours of code; doing it incorrectly misses sanctions exposure on a hidden owner. The CH-watch endpoint composes Companies House profile + officers + PSC tree + UBO walk in one call.
What the API returns for an accountant onboarding
One call to /v1/ch/companies/{number}/psc-tree returns: company name + CH number + companyStatus + active officers + filings status + PSC tree (depth 5) + UBOs at >=25% effective stake + cycle-detection flag. Each UBO carries the per-individual sanctions + PEP + adverse-media rollup so the accountant's client-acceptance memo can include the AML evidence directly. Pair with /v1/sanctions/screen for the full screen on each named director + UBO.
How accountants integrate it
Drop the endpoint into your practice-management software (Karbon, Senta, IRIS) at the new-client-creation step. The customer fills in the company number; the API call populates the rest of the form: directors, beneficial owners, registered office, latest accounts filing. The MLR-2017 evidence binds to the matter file via the audit-cert hash. Per-onboarding cost: £0.69 entry; cheaper at volume. For a 50-corporate-onboarding-per-year practice, £35/year + Stripe — well below SmartSearch's accountant-bundle floor.
PSC walk + UBO discovery in one call
The PSC walker handles up to 5 levels of UK corporate ownership with cycle detection + lower-bound stake aggregation (75% × 75% = 56.25% UBO; 50% × 25% = 12.5% NOT UBO). Control-natures (right-to-appoint-and-remove-directors etc) qualify regardless of share %. Non-UK corporate parents stop the walk at the leaf with a flag for manual review. The result is the LSAG-2025 §B-compliant beneficial-ownership picture in JSON.
Frequently asked
How deep does the PSC walk go?
Default depth 5; configurable via `?depth=N` (max 5). UK corporate parents recurse; non-UK parents stop with a `non-uk-corporate-leaf` flag for manual review.
How are UBO stakes calculated through chains?
Lower-bound aggregation: 75% × 75% = 56.25%. Control-natures qualify regardless of share %. Mirrors MLR-2017 reg 5(1)(a) + 5(1)(c).
What if the chain has a non-UK parent?
The walker stops at the non-UK leaf with a flag; the response surfaces unresolved-walk = true so the caller can flag for manual review or supplement with the foreign-registry data.
Does this cover dissolved + struck-off companies?
Yes. Companies House marks them with `companyStatus: 'dissolved'`/`'liquidation'`. The score immediately reflects status; surfaces as the top-line factor for the accountant's risk-acceptance decision.
Does it monitor the client for in-life changes?
The /v1/ch/companies/{number}/monitor endpoint adds the company to the watchlist; daily-cron diffs the PSC tree + officers + filings + alerts on changes. Subscription tier required (mirrors S1 monitoring tier).