| Sp@Ce After School Clubs Ltd | Health & social care | 2021 |
| Space Above Limited | Construction | 2015 |
| Space Building Ltd | Construction | 2022 |
| Spacetec Limited | Information & communication | 2007 |
| Spark IQ Electrical Ltd | Construction | 2026 |
| Sparked&Ready Ltd | Construction | 2026 |
| Sparkle Health Care Ltd | Public administration | 2017 |
| Sparksweld Limited | Construction | 2011 |
| Sparrow Hall Properties Limited | Real estate | 2002 |
| Spartan South Midlands Football League Limited | Administrative & support | 2015 |
| SPC Mechanical Ltd | Manufacturing | 2025 |
| SPEC85 Ltd | Professional & scientific | 2018 |
| Speed Czartrans. Ltd | Transport & logistics | 2025 |
| Speedcar Services Ltd | Wholesale & retail | 2022 |
| Speedline Taxis Dunstable Ltd | Transport & logistics | 2019 |
| Sperring Residential Limited | Real estate | 2020 |
| Speyhawk Limited | Administrative & support | 2014 |
| SPG Training Solutions Ltd | Professional & scientific | 2019 |
| Sphere Accountancy Limited | Professional & scientific | 2019 |
| Spice House MK Limited | Hospitality | 2025 |
| Spice Hub Ltd | Hospitality | 2025 |
| Spice MAX Limited | Hospitality | 2024 |
| Spice of Indian Takeaway Ltd | Hospitality | 2025 |
| Spicer & Co UK Limited | Professional & scientific | 2015 |
| SPINNERS2A Limited | Professional & scientific | 2011 |
| Spnovate Limited | Information & communication | 2025 |
| Sports.Info Limited | Extraterritorial | 2000 |
| Spotlight Security Management Limited | Administrative & support | 2011 |
| SPT Engineering Ltd | Manufacturing | 2025 |
| Square Barber Ltd | Other services | 2024 |
| Square October 1 Limited | Professional & scientific | 2004 |
| Square October 2 Limited | Professional & scientific | 2004 |
| Square October 3 Limited | Professional & scientific | 2004 |
| Square People Solutions Ltd | Information & communication | 2010 |
| Squie Limited | Information & communication | 2011 |
| Squish Delish Limited | Professional & scientific | 2016 |
| SR Safety Compliance Ltd | Professional & scientific | 2025 |
| SR Spice Limited | Hospitality | 2021 |
| Srb-Griturn Limited | Manufacturing | 1977 |
| Srishti Groups Ltd | Wholesale & retail | 2025 |
| SRJ Build Ltd | Construction | 2026 |
| SRM Trading Limited | Wholesale & retail | 2015 |
| SRS Sales & Service Ltd | Manufacturing | 2014 |
| Srs-The Development Team Limited | Professional & scientific | 2005 |
| SS Prive Ltd | Other services | 2021 |
| SS Properties Luton Limited | Real estate | 2024 |
| SS Schools HR Consultancy Ltd | Administrative & support | 2024 |
| SSA London Limited | Other services | 2015 |
| Ssamluc Builders Ltd | Construction | 2025 |
| SSK Property Investments Ltd | Real estate | 2020 |
| SSM Electrical Ltd | Construction | 2020 |
| SSN Motors Limited | Wholesale & retail | 2026 |
| SSO IT Projects Ltd | Information & communication | 2015 |
| Ssoop Ltd | Real estate | 2025 |
| Sspgt Limited | Wholesale & retail | 2025 |
| ST Albans Renovations Ltd | Construction | 2024 |
| ST Augustine's Academy Trust | Education | 2012 |
| ST Cathrines Care (Group) Limited | Other services | 2017 |
| ST George's Professional Services Limited | Administrative & support | 2013 |
| ST Mary's Court Flats Management Limited | Households | 1993 |
| ST Star Properties Ltd | Real estate | 2024 |
| Stabilo UK Limited | Arts & recreation | 2017 |
| Stafford Road 1969 Limited | Extraterritorial | 2014 |
| STAGED2SELL Ltd | Professional & scientific | 2021 |
| Stainless Balustrade Solutions Limited | Manufacturing | 2014 |
| Stalking Horse Marketing Ltd | Administrative & support | 2011 |
| Stanbridge Interiors Limited | Professional & scientific | 2006 |
| Stanley and Ingram Limited | Construction | 2020 |
| Star Capital Management Limited | Real estate | 2016 |
| Star River Group Limited | Administrative & support | 2016 |
| Starch UK Ltd | Professional & scientific | 2021 |
| Stark Creations Ltd | Administrative & support | 2011 |
| Starlight Stories Limited | Education | 2023 |
| Starling Roofing Services Limited | Construction | 2021 |
| Statefir Limited | Professional & scientific | 1979 |
| Station Road Dunstable Ltd | Professional & scientific | 2018 |
| Statstax Ltd | Information & communication | 2023 |
| Stealth Robotics Ltd | Information & communication | 2016 |
| Steel & Glass Solutions Limited | Manufacturing | 2019 |
| Steel Design Services Ltd | Professional & scientific | 2022 |
| Steele Quality Developments Ltd | Real estate | 2024 |
| Steele Quality Interiors Limited | Construction | 2019 |
| Stefan Guliga Ltd | Construction | 2023 |
| Stefanix Ltd | Transport & logistics | 2025 |
| Stefanmg Ltd | Transport & logistics | 2025 |
| Stefybrows Permanent Make UP Limited | Other services | 2025 |
| Stellar & Rose Ltd | Professional & scientific | 2024 |
| Stellar Beauty Ltd | Other services | 2023 |
| Stephan Delivery Ltd | Transport & logistics | 2026 |
| Stephen Hewitt Consulting Limited | Professional & scientific | 2013 |
| Stephen Searle Services Ltd | Administrative & support | 2016 |
| Sterling Wills Ltd | Professional & scientific | 2006 |
| Steve Moran Management Services Limited | Construction | 2016 |
| Steve Whinnett Carpentry & Joinery Ltd | Construction | 2006 |
| Steven Edwards Engineering Limited | Other services | 2005 |
| Steven Sawyer Limited | Administrative & support | 2010 |
| Steverica Ltd | Extraterritorial | 2013 |
| Stevie’S Swim School Limited | Education | 2022 |
| Stiky Trans Ltd | Transport & logistics | 2016 |
| Sting Property Ltd | Real estate | 2021 |