| Sdaccounting & Consulting Limited | Professional & scientific | 2016 |
| SDP Group UK Limited | Construction | 2026 |
| SDS Tech Solutions Limited | Real estate | 2012 |
| Sean Holdings Limited | Education | 2012 |
| Seasplit Ltd | Professional & scientific | 2021 |
| Seby Shop Ltd | Construction | 2021 |
| Second Jacobsen's Estate Management Company Limited | Construction | 1975 |
| Second Skin Agency Limited | Arts & recreation | 2012 |
| Securitas Aurum Ltd | Professional & scientific | 2018 |
| Sedgemore Limited | Real estate | 1992 |
| Seedful Limited | Manufacturing | 2014 |
| Sefton Care Limited | Real estate | 2001 |
| Sejal Consulting Limited | Professional & scientific | 2025 |
| Selectpay (Tring) Limited | Real estate | 2007 |
| Selectwell Limited | | 1985 |
| Selva Mahal Limited | Wholesale & retail | 2017 |
| Semper Crescente Properties Limited | Real estate | 2019 |
| Senator Hotels Limited | Hospitality | 1987 |
| Sensi Catering Limited | Hospitality | 2024 |
| Sequin Capital and Consultancy Limited | Professional & scientific | 2023 |
| Serj Limited | Real estate | 2006 |
| SET and Dressed Limited | Professional & scientific | 2016 |
| Set.K.N Limited | Hospitality | 2024 |
| Seven Studios Ltd | Construction | 2021 |
| Seventy Seven Studios Limited | Wholesale & retail | 2023 |
| Seymour House Investments Limited | Extraterritorial | 2009 |
| Seymour House Residential Care Homes Limited | Health & social care | 2003 |
| SGS (LDN) Ltd | Health & social care | 2022 |
| SH Medicare Ltd | Health & social care | 2023 |
| SH Tennis Asset Management Ltd | Extraterritorial | 2012 |
| Shah London Ltd | Extraterritorial | 2008 |
| Shah Management Service Limited | Professional & scientific | 2013 |
| Shah Property Holdings Limited | Real estate | 2022 |
| Shaista Lakha Photography Ltd | Professional & scientific | 2018 |
| Sharan Properties & Developments Ltd | Real estate | 2007 |
| Sharish Properties Limited | Real estate | 2010 |
| Sharp Planning and Project Controls Limited | Professional & scientific | 2025 |
| Shash Financial Limited | Professional & scientific | 2026 |
| Shasonic Galleria Limited | Wholesale & retail | 1983 |
| Shasonic Limited | Wholesale & retail | 1993 |
| Shatel International Consultancy Limited | Real estate | 2004 |
| SHC Accident Helpline Limited | Administrative & support | 2015 |
| SHC Global Property Limited | Real estate | 2024 |
| Shdc Limited | Health & social care | 2023 |
| Shelley Close (Rickmansworth) Management Company Limited | Professional & scientific | 1980 |
| Sherbanu Limited | Real estate | 2015 |
| Sherpa Financial Solutions Limited | Financial services | 2016 |
| Shezhara Ltd | Hospitality | 2021 |
| Shift Habits for Good Ltd | Professional & scientific | 2026 |
| Shift Habits Ltd | Information & communication | 2025 |
| Shining Stars Fostering Agency Limited | Health & social care | 2015 |
| Shiv U.K. Limited | Wholesale & retail | 2017 |
| Shivtej Technology Ltd | Information & communication | 2016 |
| Shomco Ltd | Information & communication | 2015 |
| Shopping Master Ltd | Wholesale & retail | 2012 |
| Shree OM Consultancy Limited | Other services | 2020 |
| Shree Siddhivinayak Property Management Ltd | Construction | 2025 |
| Shreeji Properties Investments Limited | Real estate | 2013 |
| Shreeji Reality Ltd | Real estate | 2017 |
| Shreejii Investment Ltd | Real estate | 2025 |
| Shreenath 51PEBWORTH Limited | Real estate | 2026 |
| Shreenath Investments Ltd | Financial services | 2020 |
| Shreenath Properties Limited | Real estate | 2025 |
| Shreenath UK Limited | Real estate | 2008 |
| SHZ Enterprises Limited | Information & communication | 2017 |
| SHZ Properties Limited | Real estate | 2018 |
| Siamel Ltd | Information & communication | 2022 |
| Sid'Ssolawoodflowers Ltd | Wholesale & retail | 2020 |
| Siddharth Development and Letting Limited | Real estate | 2025 |
| Siddharth Jewellery (U.K.) Limited | Construction | 2004 |
| Sienna Smiles Limited | Health & social care | 2018 |
| Sigma Signs Digital Ltd | Manufacturing | 2013 |
| Sigma Ventures Ltd | Construction | 2022 |
| SIGMA5 Limited | Wholesale & retail | 2013 |
| SIGMA5 Real Estate Limited | Real estate | 2022 |
| Signals CFO Limited | Information & communication | 2025 |
| Signature Moments Events Limited | Arts & recreation | 2023 |
| Sikdar Properties Ltd | Real estate | 2025 |
| Silicon Vision Limited | Information & communication | 1986 |
| Silleworks Ltd | Information & communication | 2025 |
| Silver Fern Supplies Ltd | Hospitality | 2011 |
| Silverlynx Limited | Other services | 2016 |
| Silverscreen Consultants Limited | Professional & scientific | 2020 |
| Silvio's Construction Ltd | Manufacturing | 2024 |
| Simpletech Consulting Limited | Information & communication | 2017 |
| Simply Food Limited | Professional & scientific | 2016 |
| Simply Microwave Limited | Hospitality | 2008 |
| Simply Veins Ltd | Health & social care | 2022 |
| Simtest Limited | Administrative & support | 2026 |
| Singercise Limited | Arts & recreation | 2019 |
| Siri Consultancy Ltd | Professional & scientific | 2024 |
| Sirius Corp Ltd | Information & communication | 2024 |
| Sirius Omega Limited | Information & communication | 2020 |
| Sisily Consulting Limited | Education | 2024 |
| Site Services and Security Limited | Administrative & support | 2013 |
| SIX Degrees Capital Group Limited | Real estate | 2018 |
| SJS Medical Limited | Administrative & support | 2014 |
| SK Reservations (UK) Limited | Administrative & support | 2023 |
| Skiiin Ltd | Wholesale & retail | 2022 |
| Skillbridge Tech Limited | Information & communication | 2026 |