How is a UK UBO calculated through layered company structures?

A UK Ultimate Beneficial Owner is calculated by walking the PSC tree and multiplying the lower-bound stake bands at each level. The MLR-2017 reg 5(1)(a) threshold is >=25% effective ownership or control. Companies House publishes share % bands not exact percentages (e.g. "75% to 100%"), so the standard practice is to use the lower bound at each level for conservative aggregation.

Worked example: ParentCo owns 75-100% of MidCo, MidCo owns 75-100% of TargetCo, an individual owns 75-100% of ParentCo. Lower-bound: 75% × 75% × 75% = 42.2% effective stake of the individual in TargetCo. That's >=25%, so the individual is a UBO.

Negative example: ParentCo owns 25-50% of TargetCo, an individual owns 25-50% of ParentCo. Lower-bound: 25% × 25% = 6.25%. Below the 25% threshold, so the individual is NOT a UBO via this chain. (The individual might still be a UBO via another chain — you have to walk every path.)

The second qualification path is reg 5(1)(c): control-natures — the right to appoint or remove directors, significant influence over decisions, control of voting rights, etc. These qualify the holder as a UBO regardless of share %. Companies House records this in the `naturesOfControl` field on each PSC entry.

For practical implementation: walk to depth 5 (covers >99% of UK structures), handle cycles with path-set tracking, mark non-UK leaves as unresolved-walk (the foreign jurisdiction's registry isn't part of UK Companies House), screen every identified UBO against sanctions + PEP + adverse media. The Stratum CH Watch API handles all of this in one call at /v1/ch/companies/{number}/psc-tree?screen=true.

Last updated 2026-05-06.