| Simply Roofing Solutions Ltd | Construction | 2013 |
| Simply Shredding (MK) Ltd | Water & waste | 2015 |
| Simply Wood Projects Ltd | Construction | 2021 |
| Simsystems Limited | Information & communication | 2015 |
| Simulation Training Limited | Professional & scientific | 2023 |
| Sinalda UK Limited | Manufacturing | 2020 |
| Sinclair Installations Limited | Professional & scientific | 2015 |
| Sinclair Sports Coaching Ltd | Arts & recreation | 2017 |
| Sine QUA NON Ltd | Extraterritorial | 2023 |
| Sineway Services Limited | Construction | 1997 |
| Singed Genius Productions Ltd. | Information & communication | 2018 |
| Singh Driving Ltd | Transport & logistics | 2025 |
| Singh Establishments Limited | Real estate | 2018 |
| Singwell Vocal Coaching Ltd | Other services | 2025 |
| Sinus Rythem Ltd | Professional & scientific | 2023 |
| Siorai Labs Ltd | Information & communication | 2025 |
| Sipra Inc Ltd | Wholesale & retail | 2020 |
| Sirius Consulting Group Ltd | Professional & scientific | 2021 |
| Sirius Property Rentals Ltd | Real estate | 2023 |
| Sirius Wealth Management LLP | | 2019 |
| Sirius Wealth Planning Ltd | Financial services | 2022 |
| Sistarz Ltd | Health & social care | 2016 |
| Sitaa Property Limited | Other services | 2026 |
| Sitaa Property Services Ltd | Real estate | 2026 |
| Site Access Management Limited | Information & communication | 2018 |
| Site Safety Works UK Ltd | Information & communication | 2026 |
| Site Supervision (UK) Limited | Construction | 1998 |
| Siteprep Consulting Ltd | Professional & scientific | 2013 |
| Siteventure Limited | Real estate | 2000 |
| Sitters Association CIC | Other services | 2025 |
| Siva NIK Limited | Construction | 2023 |
| SIX Bros Investment Ltd | Real estate | 2024 |
| SIX42GSE Limited | Wholesale & retail | 2017 |
| Sixsix Property Group Limited | Real estate | 2017 |
| Sixty Consulting Ltd | Professional & scientific | 2013 |
| Sixty Four Property Services Limited | Real estate | 2024 |
| Siyeo's Consulting Ltd | Professional & scientific | 2010 |
| SJ Rolt Consultants Limited | Administrative & support | 2025 |
| SJA Business Consulting Ltd | Professional & scientific | 2019 |
| Sjaj Properties Ltd | Real estate | 2015 |
| SJB Bodyshop Limited | Wholesale & retail | 2012 |
| SJB Mortgage Solutions Limited | Financial services | 2017 |
| SJC Enterprises Limited | Information & communication | 2011 |
| SJF Homes Ltd | Real estate | 2022 |
| SJF Interiors Limited | Professional & scientific | 2023 |
| Sjfgolfacademy Ltd | Arts & recreation | 2021 |
| Sjgroupuk Limited | Transport & logistics | 2026 |
| SJH Plant Sales Limited | Extraterritorial | 2008 |
| Sjh-All Plant Group Limited | Wholesale & retail | 2002 |
| Sjh-All Plant Holdings Limited | Financial services | 2009 |
| Sjjs Holdings Limited | Real estate | 2023 |
| SJK Healthcare Limited | Health & social care | 2025 |
| SJK Tax Services Ltd | Professional & scientific | 2021 |
| SJP Plumbing & Property Services Ltd | Construction | 2021 |
| SJR Software Ltd | Information & communication | 2021 |
| SJS Building Contractors Ltd | Construction | 2020 |
| SJS Recycling Ltd | Other services | 2023 |
| SJS Residentials Ltd | Real estate | 2024 |
| SJT Training Ltd | Education | 2022 |
| SK & Family Transport Ltd | Transport & logistics | 2022 |
| SK Beautique Ltd | Other services | 2017 |
| SK Property Investors Ltd | Real estate | 2024 |
| SKA Properties Investment Ltd | Real estate | 2024 |
| Skashh Ltd | Arts & recreation | 2022 |
| Skcm Ltd | Agriculture & fishing | 2024 |
| Skill Splendid Tech Solutions Limited | Administrative & support | 2025 |
| Skill Verse Global Ltd | Wholesale & retail | 2025 |
| Skillgrow Technologies Ltd | Information & communication | 2021 |
| SKILLS4STEM Holdings Limited | Financial services | 2020 |
| SKILLS4STEM Ltd. | Education | 2014 |
| SKILLS4STEM Qualifications Limited | Education | 2020 |
| Skin by Charlotte Limited | Other services | 2018 |
| Skin Concept by RI Ltd | Other services | 2024 |
| Skin Journey Ltd | Health & social care | 2025 |
| Skin-Fx Studios Ltd | Other services | 2022 |
| Skincolor Ltd | Manufacturing | 2026 |
| Skinny Dog Design Limited | Professional & scientific | 2003 |
| Skinulary Ltd | Information & communication | 2021 |
| Skippey Limited | Health & social care | 2025 |
| Skirmisher Systems Limited | Real estate | 2021 |
| Skore Labs Limited | Information & communication | 2014 |
| Skuznecov Ltd | Professional & scientific | 2022 |
| SKW Consultancy Limited | Health & social care | 2023 |
| Sky High Beauty Ltd | Wholesale & retail | 2025 |
| Sky Peel Ltd | Wholesale & retail | 2023 |
| Skyblok Ltd | Information & communication | 2021 |
| Skyglide Limited | Professional & scientific | 2014 |
| Skyland Contractors Limited | Construction | 2007 |
| Skyline Cabling Solutions Limited | Information & communication | 2017 |
| Skyline Infrastructure Ltd | Construction | 2025 |
| Skylite Balloons Events and Construction Ltd | Arts & recreation | 2024 |
| Skylite Balloons Limited | Arts & recreation | 2016 |
| Skynbysa Ltd | Other services | 2024 |
| Skynox Limited | Administrative & support | 2023 |
| Skyrocket Enterprises Ltd | Administrative & support | 2025 |
| Skyway Cargo Ltd | Transport & logistics | 2020 |
| SL EI Productions Ltd | Information & communication | 2023 |
| SL2 Ltd | Health & social care | 2021 |
| Slade Consulting Services Limited | Information & communication | 1996 |
| Slater Webb Ltd | Information & communication | 2015 |