| Sinik Balik Ltd | Hospitality | 2024 |
| Sinsins Ltd | Wholesale & retail | 2024 |
| Sinthiya Properties Ltd | Real estate | 2026 |
| Sionosa Airlandtrans Ltd | Manufacturing | 2026 |
| Siop Bwdin Ltd | Wholesale & retail | 2019 |
| Sipfleet Limited | Households | 1989 |
| Siples UK Services Ltd | Administrative & support | 2025 |
| SIR Michael Wilshaw Educational Services Limited | Professional & scientific | 2016 |
| SIR Toby's Beers Ltd. | Wholesale & retail | 2018 |
| SIR Toby's Events Ltd | Hospitality | 2025 |
| SIR Toby's Kitchens Ltd | Hospitality | 2024 |
| SIR Toby's Taverns Ltd. | Hospitality | 2021 |
| Sirbob Limited | Other services | 2011 |
| Siren Bidco 247 Limited | Financial services | 2026 |
| Sirim | Financial services | 2013 |
| Sirrah Scents Ltd | Manufacturing | 2021 |
| Sisl Realisations Limited | Manufacturing | 1996 |
| Sister Coffee Shop Ltd | Hospitality | 2025 |
| SIT a BIT Ltd | Manufacturing | 2019 |
| Sitara Global Ltd | Wholesale & retail | 2024 |
| Site Office Solutions Ltd | Administrative & support | 2016 |
| Site Setting OUT Ltd | Administrative & support | 2017 |
| Sitebox Ventures Ltd | Information & communication | 2021 |
| Sitebusy Limited | | 1988 |
| Sitek Resources Limited | Administrative & support | 2020 |
| Sitewise Ltd | Professional & scientific | 2026 |
| Sittingbourne Energy Limited | Professional & scientific | 2003 |
| Sivashakthi Ltd | Wholesale & retail | 2023 |
| SIX Demon Films Limited | Arts & recreation | 2010 |
| SIX Events Ltd | Hospitality | 2018 |
| SIX Eyes Collectables Ltd | Wholesale & retail | 2023 |
| SIX ROW Ltd | Wholesale & retail | 2019 |
| Sixty Fish Limited | Hospitality | 2020 |
| Sixty Minute Smiles Ltd | Other services | 2021 |
| Sixty Property Ltd | Real estate | 2015 |
| Sixty SIX Meadow Road Management Company Limited | Households | 1987 |
| Siyawareva Healthcare Limited | Health & social care | 2016 |
| Sizthai Limited | Hospitality | 2011 |
| Sizzler Pizza Ltd | Hospitality | 2021 |
| SJ Entertainment Ltd | Arts & recreation | 2024 |
| SJ Express Ltd | Transport & logistics | 2019 |
| SJ Hinds Limited | Hospitality | 2024 |
| SJ Immaculate Ltd | Other services | 2023 |
| SJ Motion Media Ltd | Information & communication | 2025 |
| Sj(Ncfc) Ltd | Other services | 2013 |
| SJA Cars Ltd | Wholesale & retail | 2023 |
| SJA Distribution Ltd | Wholesale & retail | 2022 |
| SJD Contractors Ltd | Construction | 2026 |
| SJD Traders Limited | Wholesale & retail | 2021 |
| SJG Online Ltd | Wholesale & retail | 2021 |
| SJH Lenwade Ltd | Professional & scientific | 2012 |
| SJK Consultancy (U.K.) Ltd | Professional & scientific | 2019 |
| SJM Hospitality Ltd | Hospitality | 2024 |
| SJM Print Management Ltd | Information & communication | 2020 |
| SJM Ventures Ltd | Water & waste | 2017 |
| SJS Control Systems Limited | Construction | 2008 |
| SJS Financial Management Services Limited | Professional & scientific | 2015 |
| SJS Properties Norfolk Ltd | Construction | 2024 |
| Sjsoptical Limited | Health & social care | 2019 |
| SJV Properties Limited | Real estate | 2020 |
| SK Birmingham Ltd | Hospitality | 2016 |
| SK Construction (Norfolk) Limited | Hospitality | 2021 |
| SK Diagnostic Radiology Limited | Health & social care | 2023 |
| SK Holding Investments Limited | Real estate | 2022 |
| Skale Construction Ltd | Construction | 2017 |
| Skandinavian Dream Boat Ltd | Information & communication | 2015 |
| Skara Brae Limited | Professional & scientific | 2015 |
| SKB Import & Export Ltd | Manufacturing | 2025 |
| Skelton Projects Ltd | Professional & scientific | 2012 |
| Skeyeware Ltd | Wholesale & retail | 2023 |
| SKI Yodl Ltd | Information & communication | 2018 |
| Skillbank Solutions Limited | | 2009 |
| Skilled Futures Ltd | Education | 2025 |
| Skills Edge Training Ltd | Professional & scientific | 2009 |
| Skim RC Racing Ltd | Wholesale & retail | 2025 |
| Skin & Tonic Aesthetics Limited | Extraterritorial | 2019 |
| Skin Surgery Partnership Limited | Health & social care | 2020 |
| Skinkare Limited | Wholesale & retail | 2020 |
| Skinplicity Ltd | Other services | 2026 |
| Skipcoin Ltd | Administrative & support | 2025 |
| Skipper Recruit Limited | Administrative & support | 2020 |
| Skipwith Consulting Limited | Wholesale & retail | 2018 |
| Skivvies Torbay Handyman Services Ltd | Administrative & support | 2017 |
| SKM Assessments Limited | Professional & scientific | 2020 |
| SKM Building Products Ltd | Wholesale & retail | 2015 |
| SKM Property Limited | Real estate | 2017 |
| Skogeng Ferry Ltd | Hospitality | 2026 |
| Skogeng Hospitality Ltd | Hospitality | 2024 |
| SKS Electrical Limited | Administrative & support | 2014 |
| SKS First Limited | Financial services | 2022 |
| SKS Property (Norfolk) Ltd | Real estate | 2023 |
| SKS Wholesale Limited | Wholesale & retail | 2010 |
| Skweeky Clean Ltd. | Administrative & support | 2022 |
| Sky Apartments.Com Ltd | Hospitality | 2019 |
| Sky Barber Shop NR15 Ltd | Other services | 2025 |
| Sky Estate Rentals Limited | Real estate | 2020 |
| Sky Flights (Mc/R) Ltd | Administrative & support | 2018 |
| Sky Photographics Limited | Arts & recreation | 2015 |
| Sky Photos Limited | Arts & recreation | 2015 |
| Sky Rocket Property Investments Limited | Households | 2025 |