| Secta Investments Ltd | Wholesale & retail | 2003 |
| Securahome UK Ltd | Administrative & support | 2019 |
| Securatex Ltd. | Administrative & support | 2025 |
| Secure Alarms Systems Limited | Administrative & support | 2012 |
| Secure Payment Ltd | Wholesale & retail | 2024 |
| Secure Screening Services Ltd | Information & communication | 2018 |
| Secure Transaction Limited | Wholesale & retail | 2025 |
| Security Bonds Limited | Financial services | 2018 |
| Security Investigations Ltd | Wholesale & retail | 2020 |
| Securwright Ltd | Information & communication | 2025 |
| Sedr Insight Limited | Information & communication | 2010 |
| Seecloud Limited | Information & communication | 2016 |
| Seed Housing Ltd | Real estate | 2024 |
| Seed Mentors Limited | Professional & scientific | 2012 |
| Seeds and Carry Limited | Education | 2022 |
| Seedstone Group Limited | Financial services | 2025 |
| Seen + Heard C.I.C. | Health & social care | 2024 |
| Seen Outdoor Limited | Professional & scientific | 2024 |
| Seenite Limited | Professional & scientific | 2008 |
| Seerswhite Limited | Construction | 2018 |
| Segensworth Access Road Limited | Extraterritorial | 2022 |
| Seggie Holdings Ltd | Real estate | 2020 |
| Selah BR Limited | Wholesale & retail | 2025 |
| Selano Group Limited | Wholesale & retail | 2025 |
| Select Aviation Ltd | Transport & logistics | 2024 |
| Select Group Recruitment Ltd | Administrative & support | 2021 |
| Select Investment Services Limited | Administrative & support | 2004 |
| Select Partners Ltd | Real estate | 2025 |
| Select Publisher Services Limited | Information & communication | 2005 |
| Select Pumps Limited | Manufacturing | 2004 |
| Select Resin Ltd | Construction | 2021 |
| Select Trading Ltd | Wholesale & retail | 2025 |
| Self Kair Ltd | Wholesale & retail | 2021 |
| Selfinity AI Limited | Information & communication | 2026 |
| Selin & Emir Ltd | Hospitality | 2018 |
| Selline Limited | Wholesale & retail | 2025 |
| Selny Ltd | Information & communication | 2023 |
| Semarchy Limited | Information & communication | 2014 |
| Semibreve Software Ltd | Information & communication | 2024 |
| Semvertex Dynamics Ltd | Manufacturing | 2025 |
| Senary Labs Ltd | Information & communication | 2023 |
| Senator Care Ltd | Extraterritorial | 2006 |
| Sendero Training Ltd | Education | 2018 |
| Senlan Securities Limited | Real estate | 1971 |
| Sennagoat Ltd | Wholesale & retail | 2026 |
| Senngroup Limited | Wholesale & retail | 2025 |
| Senryaku Labs Limited | Information & communication | 2024 |
| Sensibl Ltd | Manufacturing | 2019 |
| Sensory TOYS4U Ltd | Education | 2022 |
| Sentinel Court Limited | Households | 2014 |
| Sentinel Electrical Solutions Limited | Construction | 2025 |
| Sentinel Facilities & Services Ltd | Construction | 2020 |
| Sentinel Fire and Security Solutions Limited | Professional & scientific | 2016 |
| Sentinel Secure Services Ltd | Other services | 2013 |
| Sentinel Sporting Services Limited | Other services | 2024 |
| Sentinel Unmanned Limited | Other services | 2016 |
| Sentosa Designs Ltd | Education | 2022 |
| Separator Spares International (UK) Ltd | Administrative & support | 2007 |
| Sephton Park Fund I L.P. | | 2007 |
| Sequoia Coaching Ltd | Professional & scientific | 2021 |
| Seraphius Ltd | Wholesale & retail | 2025 |
| Serel Limited | Hospitality | 2019 |
| Serene Holiday Services Ltd | Administrative & support | 2022 |
| Serene LL Ltd | Professional & scientific | 2015 |
| Serene Skin Aesthetics Ltd | Other services | 2026 |
| Serene Utopia Getaways Ltd | Hospitality | 2023 |
| Serenity Poole Ltd | Households | 2022 |
| Serenity Space Ltd | Hospitality | 2021 |
| Sergio Farina Ltd | Information & communication | 2025 |
| Sergio Sinks Limited | Wholesale & retail | 2019 |
| Serhacertener Limited | Real estate | 2020 |
| Seri Designs Ltd | Professional & scientific | 2017 |
| Serialised Limited | Information & communication | 2024 |
| Series Three Ltd | Information & communication | 2017 |
| Serious Privacy Ltd | Information & communication | 2017 |
| Seriously Inclusive Limited | Professional & scientific | 2020 |
| Serpsketch Ltd | Information & communication | 2019 |
| Serum Lake Ltd | Financial services | 2024 |
| Serum Lake Productions Ltd | Information & communication | 2024 |
| Serum Lake Publishing Ltd | Information & communication | 2025 |
| Service Office Ltd | Professional & scientific | 2012 |
| Serviceoversea Ltd | Wholesale & retail | 2025 |
| Services JG Ltd | Health & social care | 2024 |
| Servicetechnik Elektro Ltd | Manufacturing | 2021 |
| Servo Components & Systems Limited | Other services | 1992 |
| SES IP Holdings Limited | Financial services | 2019 |
| Settle Studio Limited | Professional & scientific | 2020 |
| Sety Digital Limited | Wholesale & retail | 2025 |
| Seven BR Limited | Wholesale & retail | 2025 |
| Seven Dials Consulting Ltd | Professional & scientific | 2018 |
| Seven Seas Network Ltd | Information & communication | 2023 |
| Seventh Vegan Limited | Wholesale & retail | 2020 |
| Sevets Construction Limited | Construction | 2017 |
| SEX With a Difference C.I.C. | Education | 2014 |
| Sextons Legal Costs Limited | Administrative & support | 2016 |
| Seyward Windows Ltd | Extraterritorial | 2012 |
| SEZ Design Ltd | Wholesale & retail | 2021 |
| SF1550 Ltd | Professional & scientific | 2026 |
| Sfbh Ltd | Information & communication | 2015 |
| SG Legal Ltd | Professional & scientific | 2025 |