| Simon Nicholas People Limited | Other services | 2017 |
| Simon Productions Limited | Information & communication | 2013 |
| Simon Shindi Limited | Hospitality | 2023 |
| Simon Smith Electrical Limited | Construction | 2013 |
| Simon Spencer Limited | Real estate | 1986 |
| Simona Tanase Research Consultancy Limited | Professional & scientific | 2022 |
| Simons Holdings Limited | Financial services | 2023 |
| Simons of London Limited | Wholesale & retail | 2014 |
| Simonsays Ltd. | Real estate | 2018 |
| Simonsays! Childcare and Franchise Group Ltd | Education | 2017 |
| Simpkin Burley Ltd | Professional & scientific | 2017 |
| Simplaystudio Ltd | Information & communication | 2016 |
| Simple Brix Ltd | Construction | 2020 |
| Simple Funerals Limited | Extraterritorial | 2005 |
| Simple Marketing Consultancy Limited | Professional & scientific | 2014 |
| Simplequicksystem.Com Ltd | Education | 2025 |
| Simpley the Best Health Care Limited | Health & social care | 2019 |
| Simplicity Small Spaces Ltd | Construction | 2018 |
| Simplify Media Ltd | Information & communication | 2024 |
| Simplifyd Ltd | Extraterritorial | 2024 |
| Simplor Ltd | Hospitality | 2023 |
| Simply Aesthetics Limited | Health & social care | 2008 |
| Simply Bricks Limited | Real estate | 2015 |
| Simply Dance Midlands Ltd | Arts & recreation | 2021 |
| Simply Desserts Notts Ltd | Hospitality | 2025 |
| Simply FED Limited | Hospitality | 2014 |
| Simply Good Tech Ltd | Information & communication | 2024 |
| Simply Leasing Limited | Extraterritorial | 2016 |
| Simply Luxe Limited | Wholesale & retail | 2015 |
| Simply Pizza & Chicken Ltd | Hospitality | 2023 |
| Simply Resilience Limited | Professional & scientific | 2016 |
| Simply Sauce Limited | Professional & scientific | 2019 |
| Simply Smiles Ahead Ltd | Health & social care | 2013 |
| Simply Spares and Consumables Limited | Wholesale & retail | 2018 |
| Simply Spice Ltd | Hospitality | 2025 |
| Simply Sport Management Limited | Arts & recreation | 2011 |
| Simply Stock Limited | Wholesale & retail | 2025 |
| Simply Sweet Supplies Ltd | Hospitality | 2025 |
| Simply Thrilled Ltd | Arts & recreation | 2019 |
| Simply Twenty One Limited | Financial services | 2021 |
| Simply Unique MAG Limited | Information & communication | 2020 |
| Simply Unique Properties Ltd | Real estate | 2025 |
| Simpson Brothers Limited | Construction | 1981 |
| Simpson Heating Limited | Construction | 2018 |
| Simpsonite Detail Specialist Ltd | Administrative & support | 2025 |
| Simpull Limited | Real estate | 2015 |
| Simran House Ltd | Real estate | 2026 |
| Simscorp Industries Ltd | Information & communication | 2021 |
| Simsey's Bathrooms Ltd | Construction | 2026 |
| Simtar Limited | Real estate | 2021 |
| Simuli Ltd | Manufacturing | 2020 |
| Simulo Limited | Professional & scientific | 2011 |
| SIN90 Ltd | Professional & scientific | 2023 |
| Sinaloa Investments Limited | Real estate | 2025 |
| Sinan Construction Limited | Construction | 2025 |
| Sinbad Homes Ltd | Real estate | 2025 |
| Sinbad Plant Limited | Construction | 1966 |
| Sinbad Tools Limited | Construction | 1976 |
| Sinclair Advisory Ltd | Information & communication | 2026 |
| Sinclair Research Limited | Information & communication | 2025 |
| Sincom Limited | Professional & scientific | 2014 |
| Sincreon Ltd | Administrative & support | 2025 |
| Sindy B Communications Limited | Professional & scientific | 2010 |
| Sinega Ltd | Hospitality | 2021 |
| Sinemas Limited | Information & communication | 2022 |
| Sinematic Ltd | Information & communication | 2025 |
| Sing Choir Ltd | Arts & recreation | 2016 |
| Singcontinuum Limited | Wholesale & retail | 2026 |
| Singh & Singh's Properties Ltd | Real estate | 2018 |
| Singh Aggregates Ltd | Transport & logistics | 2025 |
| Singh Electrical Ltd | Construction | 2022 |
| Singh Homecare Services Ltd | Administrative & support | 2024 |
| Singh Joinery Ltd | Construction | 2023 |
| Singh Sandhu Properties Limited | Real estate | 2025 |
| Singh's & Singh's Holding Limited | Administrative & support | 2025 |
| Singhcor Investments Ltd | Real estate | 2024 |
| Single & Mingle Ltd | Professional & scientific | 2023 |
| Sinin Thai Massage & Spa Ltd | Other services | 2021 |
| Sinister Intentions Ltd | Information & communication | 2024 |
| Sinnit Ltd | Transport & logistics | 2025 |
| Sinoll Limited | Wholesale & retail | 2020 |
| Sinprisa Ltd | Real estate | 2026 |
| Siobhan Goodacre Limited | Financial services | 2009 |
| Sion Electrics Ltd | Construction | 2019 |
| Sion Property Managements Ltd | Real estate | 2026 |
| SIP & Socialize Ltd | Hospitality | 2024 |
| Siphon Bros Ltd | Professional & scientific | 2024 |
| Sipping Boba City Limited | Hospitality | 2025 |
| Sipping Boba Ltd | Hospitality | 2026 |
| Sipping Station Ltd | Wholesale & retail | 2025 |
| Sira Sustainability Ltd | Professional & scientific | 2022 |
| Siraaj Studios Ltd | Information & communication | 2025 |
| Siraj Medical Limited | Health & social care | 2011 |
| Siren Furniture Limited | Wholesale & retail | 2000 |
| Siren Italia Limited | Extraterritorial | 2022 |
| Sirius Resolutions Ltd | Transport & logistics | 2025 |
| Sirkus Limited | Arts & recreation | 2002 |
| Sirsa Co Limited | Hospitality | 2025 |
| Sisco Motors Ltd | Wholesale & retail | 2017 |
| Sister P Services Limited | Health & social care | 2017 |