| Seabrook Developments Ltd | Construction | 1998 |
| Seafarer Repatriation Flights Limited | Administrative & support | 2020 |
| Seagull Media House CIC | Information & communication | 2026 |
| Seamossprofessional Ltd | Wholesale & retail | 2023 |
| Sean Rowe Limited | Professional & scientific | 2001 |
| SEARCH4STAFF Recruitment Limited | Administrative & support | 2016 |
| Searchwells Limited | Administrative & support | 2006 |
| Season-It Limited | Manufacturing | 2021 |
| Seasoned Mowing Limited | Administrative & support | 2025 |
| Seating Design & Development Limited | Financial services | 2003 |
| Seax (Meldreth) Limited | Professional & scientific | 2023 |
| Seax Development Limited | Construction | 2023 |
| Seax Trading Limited | Professional & scientific | 2017 |
| SEC Bodywork’S Ltd | Wholesale & retail | 2026 |
| Seccen Limited | Professional & scientific | 2026 |
| Second Curve Ltd | Administrative & support | 2014 |
| Second Planet From the Sun Limited | Real estate | 2007 |
| Second Steps - Burnt Mills Ltd | Health & social care | 2018 |
| Second Steps Day Nursery (Althorne) Ltd | Health & social care | 2021 |
| Second Steps Day Nursery (Colchester) Limited | Health & social care | 2017 |
| Second Steps Day Nursery (Hanningfield) Limited | Health & social care | 2023 |
| Second Steps Day Nursery (Hatfield Peverel) Limited | Health & social care | 2025 |
| Second Steps Group Limited | Financial services | 2022 |
| Second Steps Properties Limited | Real estate | 2022 |
| Section 31 Holdings Ltd | Financial services | 2021 |
| Section 31 Solutions Ltd | Other services | 2021 |
| Securegravity Labs Ltd | Information & communication | 2025 |
| Securemed Ltd | Transport & logistics | 2022 |
| Security Mortgage Services Ltd | Financial services | 2005 |
| Security Solutions Group Limited | Administrative & support | 2024 |
| Sedera Ltd | Information & communication | 2016 |
| SEE My GP Ltd | Health & social care | 2025 |
| Seelig Partners Limited | Professional & scientific | 2011 |
| Seelycrozier Plastering Ltd | Construction | 2020 |
| Seem Events Ltd | Other services | 2024 |
| Seferi Steel Work Ltd | Construction | 2022 |
| Seferi Valeting Services Ltd | Wholesale & retail | 2021 |
| Sehyog 11PLUS Limited | Education | 2022 |
| Sehyog Academy Limited | Education | 2023 |
| Sehyog EDU Limited | Education | 2022 |
| Sekhar Abraham Photography Limited | Professional & scientific | 2025 |
| Selech Data Services Limited | Information & communication | 1996 |
| Select Cleaning Group Limited | Administrative & support | 2020 |
| Select Engineering Limited | Administrative & support | 1992 |
| Select Engineering Trustee Limited | Professional & scientific | 2021 |
| Select Offshore Ltd | Administrative & support | 2013 |
| Select OIL and GAS Limited | Extraterritorial | 2013 |
| Select Sealants Limited | Construction | 2010 |
| Select Tech Ltd | Information & communication | 2015 |
| Select Thermal Ltd | Construction | 2024 |
| Selene Marine UK Limited | Information & communication | 2015 |
| Self Defence Training Systems Ltd | Education | 2021 |
| Selfmart Limited | Other services | 2025 |
| SEN Diagnostics Limited | Health & social care | 2014 |
| Senbla Productions Ltd | Arts & recreation | 2018 |
| Sense Building Solutions Ltd | Construction | 2016 |
| Sensore Ltd | Professional & scientific | 2020 |
| Sentio Healthcare Transformation Limited | Professional & scientific | 2020 |
| Sentio Limited | Real estate | 2001 |
| SEO Matthew Limited | Professional & scientific | 2026 |
| Sephra Ltd | Transport & logistics | 2018 |
| Sequential Thinking Limited | Administrative & support | 2014 |
| Serene Living Spaces Ltd | Hospitality | 2023 |
| Serenity Developers Limited | Construction | 2026 |
| Serenity Pathways Counselling Limited | Health & social care | 2025 |
| Serenity Residential Holdings Limited | Real estate | 2026 |
| Seriesmedia Solutions Ltd | Information & communication | 2023 |
| Serpica Limited | Construction | 1997 |
| Serrot Trading Limited | Administrative & support | 2011 |
| Service Charge Analytics Ltd | Professional & scientific | 2019 |
| Service Company Creator Ltd | Education | 2024 |
| Service Hotels 2 Limited | Financial services | 2015 |
| Service Hotels Limited | Construction | 1960 |
| Service on Site Limited | Wholesale & retail | 2001 |
| Services Equipment and Spares Limited | Wholesale & retail | 1986 |
| Sesom Projects Limited | Real estate | 2022 |
| Seth Logistics UK Limited | Transport & logistics | 2019 |
| Sethmaal Limited | Health & social care | 2023 |
| Sevco 5533 Limited | Professional & scientific | 2002 |
| Seven ASH Advisers Limited | Professional & scientific | 2015 |
| Seven Distribution Limited | Wholesale & retail | 2012 |
| Seven Distribution UK Ltd | Wholesale & retail | 2017 |
| Seven Sisters Partners Ltd. | Financial services | 2025 |
| Sevenoaks Electrical (South East) Limited | Manufacturing | 2014 |
| Sevenplatform V Limited | Financial services | 2021 |
| Seventh Acorn Limited | Administrative & support | 1995 |
| Sewell Flower Shop Limited | Wholesale & retail | 2021 |
| Sewell's Finance Ltd | Professional & scientific | 2022 |
| Sewing Solutions Limited | Manufacturing | 2016 |
| Seymour & Sons Electrical Limited | Construction | 2020 |
| Seymour House Ltd. | Education | 1987 |
| Seymour Street Residents Association Limited | Households | 1998 |
| Seza Management Consultants Ltd | Professional & scientific | 2022 |
| SFA Advisory Services Limited | Other services | 2010 |
| SFF Electrical Limited | Construction | 2022 |
| SFH Properties Limited | Real estate | 2020 |
| SFL Consultancy Limited | Professional & scientific | 2020 |
| SFS Properties Limited | Real estate | 2018 |
| SG Engineering 86 Ltd | Manufacturing | 2019 |
| SGC Backoffice Ltd | Professional & scientific | 2019 |