How is a UK UBO calculated under MLR-2017?

Under MLR-2017 reg 5(1)(a), an Ultimate Beneficial Owner (UBO) is an individual with 25%+ effective ownership or voting rights in a UK company, calculated through any chain of intermediate corporate owners. The walk multiplies stakes through the chain: a person holding 75% of Co A, which holds 75% of Co B, has a 56.25% effective stake in Co B (75% × 75%) and is therefore a UBO. Someone holding 50% of Co A which holds 25% of Co B has a 12.5% effective stake and is NOT a UBO of Co B.

Reg 5(1)(c) adds a parallel test: an individual exercising significant control through means other than ownership (right to appoint or remove a majority of directors, ability to exercise significant influence) is also a UBO regardless of share percentage. This catches trustee structures, golden-share arrangements, and shadow directors.

For letting agents and accountants under LSAG-2025 / MLR-2017, the practical workflow is: for a corporate client or corporate landlord, pull the Companies House PSC (Persons with Significant Control) record, walk the tree to identify all individuals at 25%+ effective stake, identify any control-rule UBOs (reg 5(1)(c)), then screen each named UBO against sanctions, PEP, and adverse-media sources. The walk needs to handle cycles (companies cross-owning each other) and depth caps (industry standard is depth 5; corporate structures rarely meaningfully deeper).

Certaby's letting-agent and conveyancer suites handle the PSC walk automatically when the corporate landlord or seller field is populated. Each UBO appears as a row in the audit-cert PDF with their effective stake, the chain that produced it, and their individual screen result.

Source: HMRC PSC Guidance

Last updated 2026-05-09.