| Sideslip Ltd | Information & communication | 2018 |
| Sidonis Express Limited | Information & communication | 2025 |
| Sidontex Commercial LP | | 2013 |
| Sienna and Giorgia Limited | Hospitality | 2026 |
| Sierra Bay SP | | 2005 |
| Sierra Partners, L.P. | | 2020 |
| Sierra Sunrise Ltd | Financial services | 2024 |
| Siesta Key LP | | 2001 |
| Siexec 8020 Limited | Financial services | 2020 |
| SIF 2A Partners LP | | 2021 |
| SIG 1 Holdings Limited | Financial services | 1993 |
| SIG Inc. LP | | 2013 |
| SIG Number 2 Limited | Financial services | 2010 |
| Sighthill News Ltd | Wholesale & retail | 2026 |
| Sighthill Supermarket Ltd | Wholesale & retail | 2020 |
| Sights & Attractions LP | | 2013 |
| Sigma (Northern) Founder Partner LP | | 2019 |
| Sigma Alliance LP | | 2015 |
| Sigma Alpha MU LP | | 2001 |
| Sigma Business LP | | 2016 |
| Sigma Capital Property Ltd | Real estate | 2001 |
| Sigma Founder Partner Limited Partnership | | 2014 |
| Sigma FP General Partner Limited | Real estate | 2014 |
| Sigma General Partner Limited | Real estate | 2014 |
| Sigma Infocom Limited | Information & communication | 2006 |
| Sigma Inpartnership Ltd | Real estate | 2000 |
| Sigma Private Office Limited | Financial services | 1997 |
| Sigma Property Partners Limited | Real estate | 2014 |
| Sigma PRS Developments Limited | Real estate | 2015 |
| Sigma PRS Founder Partner LP | | 2016 |
| Sigma PRS General Partner LLP | | 2016 |
| Sigma PRS GP Limited | Real estate | 2015 |
| Sigma PRS Investments I Limited | Real estate | 2015 |
| Sigma PRS Properties LP | | 2016 |
| Sigma Survey and Design Ltd | Professional & scientific | 2015 |
| Sigma Sustainable Energy Fund II L.P. | | 2007 |
| Sigma TEN Limited | Health & social care | 2017 |
| Sigma Thistle Phase II FP LP | | 2015 |
| Sigma Thistle Phase II GP LLP | | 2015 |
| Sigma Thistle Phase II Limited | Real estate | 2015 |
| Sigma Trade Power LP | | 2015 |
| Sigma Zoom LP | | 2016 |
| Sigma-Lauren Limited | Wholesale & retail | 2018 |
| Sigmal LP | | 2013 |
| Sigmalab Limited | Information & communication | 2020 |
| Sigmatrade Corporation LP | | 2017 |
| Sign Translation Limited | Administrative & support | 2021 |
| Signal & Secure Living Ltd | Construction | 2023 |
| Signal Vector LP | | 2025 |
| Signallus Ltd | Information & communication | 2026 |
| Signature Autos Edinburgh Ltd | Wholesale & retail | 2024 |
| Signature Barbershop Southside Ltd | Other services | 2018 |
| Signature Bookkeeping - Ksiegowosc Ltd | Professional & scientific | 2023 |
| Signature Building & Paving Ltd | Construction | 2023 |
| Signature Cars Edinburgh Ltd | Wholesale & retail | 2024 |
| Signature Finishes Limited | Construction | 2014 |
| Signature Flight Support UK Regions Limited | Administrative & support | 1996 |
| Signature Thai Clinic Ltd | Health & social care | 2024 |
| Signer Limited | Arts & recreation | 2012 |
| Signergy Ltd | Manufacturing | 2021 |
| Signet Mercantile Limited | Hospitality | 2023 |
| Signet Protocol Ltd | Information & communication | 2026 |
| Signet Sales L.P. | | 2010 |
| Signetco Limited | Hospitality | 2021 |
| Signport Ltd | Professional & scientific | 2024 |
| Signwow Global Ltd | Financial services | 2024 |
| Signwow Limited | Administrative & support | 2022 |
| Sigoge LP | | 2013 |
| Sigr Ltd | Information & communication | 2025 |
| Sigtuna (Europe) LP | | 2013 |
| Siguler Guff Kinea Holdings, LP | | 2018 |
| Sikasa Ltd | Professional & scientific | 2020 |
| Sikh Sanjog | Administrative & support | 1999 |
| Sila Group Ltd | Construction | 2022 |
| Silaki Ltd | Hospitality | 2025 |
| Silassio Industries LP | | 2013 |
| Silberline Limited | Manufacturing | 1974 |
| Silent Adventures Ltd | Administrative & support | 2017 |
| Silent Format LP | | 2025 |
| Silentium Limited | Hospitality | 2025 |
| Silica Verse Ltd | Construction | 2026 |
| Silicon Access L.P. | | 2011 |
| Silicon II Access L.P. | | 2011 |
| Siliconglen Ltd | Information & communication | 2001 |
| Siliconsea LP | | 2023 |
| Silk Purse Sow's EAR Ltd | Wholesale & retail | 2021 |
| Silk Road Capital LP | | 2016 |
| Silk Road Tourism LP | | 2016 |
| Silk Road Travel LP | | 2016 |
| Silktop Limited | Wholesale & retail | 2025 |
| Silky Motors Ltd | Wholesale & retail | 2016 |
| Silky Pickle Ltd | Hospitality | 2018 |
| Sillage LP | | 2025 |
| Sillerton Climate Ltd | Professional & scientific | 2025 |
| Sillmarion LP | | 2015 |
| Siltex Business LP | | 2015 |
| Siltex Universal LP | | 2014 |
| Silton Forestry Ltd | Agriculture & fishing | 2024 |
| Silux LP | | 2014 |
| Silva Group LP | | 2015 |