| Smart Sapphire Ltd | Real estate | 2014 |
| Smart Tech Rickmansworth Ltd | Wholesale & retail | 2023 |
| Smart Value Limited | Professional & scientific | 2012 |
| Smart.B Ltd | Other services | 2024 |
| Smartcards Limited | Manufacturing | 1998 |
| Smarter Scoring Limited | Information & communication | 2022 |
| Smdg Residential Ltd | Real estate | 2024 |
| SMG Property Solutions LLP | | 2025 |
| Smith Services Group Limited | Construction | 2023 |
| Smith-Milne & Co. Limited | Professional & scientific | 2006 |
| Smoothflow Commissioning Ltd | Construction | 1996 |
| Smoothflow Limited | Financial services | 2002 |
| Smoothflow Trustees Limited | Administrative & support | 2020 |
| Smoothflow Water Treatment Limited | Construction | 2004 |
| Smoothflow Water Treatments Limited | Extraterritorial | 2005 |
| SN Dyslexia & Dyscalculia Services Ltd | Education | 2023 |
| SN ISW Services Ltd | Health & social care | 2021 |
| Snack in the Mouth Limited | Hospitality | 2026 |
| SNC Homes Ltd | Real estate | 2024 |
| SND Global Ltd | Wholesale & retail | 2023 |
| SNJ Residential Ltd | Real estate | 2019 |
| Snowdon Tate Ltd | Administrative & support | 2005 |
| Soblo Ltd | Wholesale & retail | 2018 |
| Socio Technical Systems Limited | Administrative & support | 2012 |
| Sofeminine.Co.Uk. Limited | Information & communication | 2008 |
| Soffelle Ltd | Administrative & support | 2026 |
| Softcloud Ltd | Information & communication | 2014 |
| SOL2LIN Limited | Information & communication | 2013 |
| Solarbrite Limited | Manufacturing | 1987 |
| Solesbridge Consulting Limited | Professional & scientific | 2024 |
| Solidified Ltd | Education | 2024 |
| Solutionsmtd Ltd | Professional & scientific | 2005 |
| Solved Marketing Ltd | Professional & scientific | 2024 |
| Soma Autos Ltd | Wholesale & retail | 2020 |
| Somatic Therapy Ltd | Health & social care | 2022 |
| Somma+ Ltd | Professional & scientific | 2025 |
| Soonam Ltd | Wholesale & retail | 2020 |
| Sopure London Limited | Wholesale & retail | 2018 |
| Sothea Holdings Ltd | Other services | 2022 |
| Soulitude Functional Health Ltd | Health & social care | 2025 |
| Sound Mouth Limited | Professional & scientific | 2008 |
| Sound Supply Events Ltd | Other services | 2018 |
| Southglobe Limited | Professional & scientific | 1983 |
| Southpaw Creative Limited | Professional & scientific | 2012 |
| SP Advisors Limited | Professional & scientific | 2023 |
| SP Property Consultancy Limited | Administrative & support | 2025 |
| SP2 Accounting Limited | Professional & scientific | 2017 |
| Spap Shine Ltd | Health & social care | 2023 |
| Sparaton (Abchurch Yard) Limited | Hospitality | 2019 |
| Sparkles Lighting Ltd | Construction | 2022 |
| Spartac Contractors Ltd | Construction | 2013 |
| Spec Designer Limited | Information & communication | 2010 |
| Spectrum Assets Ltd | Financial services | 2026 |
| Spectrum Lighting Ltd | Administrative & support | 2020 |
| Spectrum Painting Ltd | Construction | 2020 |
| Speeble Ltd | Health & social care | 2019 |
| Speed Engines Motors Ltd | Wholesale & retail | 2026 |
| Spencer & Co. Estates Limited | Real estate | 2012 |
| Spfm Ltd | Administrative & support | 2021 |
| Sphaira Limited | Construction | 2020 |
| Sphere Production Solutions Ltd | Administrative & support | 2026 |
| Spice Staples Limited | Manufacturing | 2026 |
| Spice Studios International Ltd | Wholesale & retail | 2015 |
| Splatworks Limited | Wholesale & retail | 2021 |
| Sports Cast Ltd | Information & communication | 2025 |
| Spring AI Ltd | Information & communication | 2025 |
| Spring Surveying Services Limited | Professional & scientific | 2020 |
| Springfield Court Rickmansworth RTM Company Limited | Households | 2014 |
| Springstate Limited | Arts & recreation | 2022 |
| Springtime Properties Limited | Real estate | 2002 |
| Springwell Lane Metal Recycling Limited | Water & waste | 2023 |
| Spru Rowland Limited | Information & communication | 2011 |
| SPS Nottingham Limited | Real estate | 2018 |
| SPS Property Services Limited | Construction | 2011 |
| SPS UK Investments Limited | Financial services | 2018 |
| SPW Plant London Ltd | Construction | 2024 |
| Square Root Trading Ltd | Wholesale & retail | 2021 |
| Squarebox - Smart Accounting Software Ltd | Information & communication | 2018 |
| Squires Enteprise Limited | Hospitality | 2022 |
| SR Dental Laboratory Limited | Manufacturing | 2023 |
| Sree Technologies Limited | Information & communication | 2009 |
| SRI Pendyala Limited | Information & communication | 2014 |
| Srisriram Ltd | Wholesale & retail | 2020 |
| SRP Investments Limited | Real estate | 2000 |
| SS Clinic London Limited | Other services | 2025 |
| SS Media Limited | Manufacturing | 2007 |
| SSJ Associates Limited | Professional & scientific | 2023 |
| Sskn London Ltd | Manufacturing | 2026 |
| Ssln Properties Ltd | Real estate | 2021 |
| SSR Estates Limited | Real estate | 2012 |
| ST Albans Car Sales Ltd | Wholesale & retail | 2014 |
| ST Georges Facilities and Supply Chain Management Limited | Real estate | 2024 |
| ST Helier Group Limited | Construction | 2023 |
| ST Merc Ltd | Wholesale & retail | 2021 |
| Stacdene Holdings Limited | Real estate | 2008 |
| Stag Global Ltd | Professional & scientific | 2024 |
| Staggering Wines Limited | Wholesale & retail | 1998 |
| Stanciu Transport Services Limited | Transport & logistics | 2018 |
| Star Accounting Limited | Professional & scientific | 2023 |
| Star Counselling Limited | Health & social care | 2019 |