| Seckloe 330 Limited | Administrative & support | 2007 |
| Seckloe 402 Limited | Information & communication | 2008 |
| Seckloe 50 Limited | Wholesale & retail | 2000 |
| Second ROW Limited | Wholesale & retail | 2021 |
| Second Story Boutique Ltd | Wholesale & retail | 2026 |
| Second Vision Limited | Professional & scientific | 2019 |
| Secrets to Beauty Ltd | Other services | 2022 |
| Sector Chelsea Ltd | Professional & scientific | 2025 |
| Secure Code Warrior Limited | Professional & scientific | 2013 |
| Secure Communications Limited | Information & communication | 2019 |
| Secure Delivery Services UK Ltd | Transport & logistics | 2018 |
| Secure Direct Ltd | Professional & scientific | 2025 |
| Secure Door 24 Limited | Manufacturing | 2025 |
| Secure Living Limited | Wholesale & retail | 2002 |
| Secure Locksmiths Limited | Construction | 2015 |
| SECURE4SHAW Ltd | Administrative & support | 2019 |
| Secureidyll Property Management Limited | Households | 2001 |
| Securifire Systems Ltd | Other services | 2018 |
| Security and Event Services Limited | Administrative & support | 2020 |
| Security Credit Bureau Limited | Financial services | 2010 |
| Security Distribution Ltd | Wholesale & retail | 2009 |
| Security SB Ltd | Administrative & support | 2020 |
| Securtex Ltd | Administrative & support | 2023 |
| Sedborough Estates Limited | Other services | 2017 |
| Sedgebrook Ltd | Real estate | 2021 |
| SEE Building Contractors Limited | Construction | 2012 |
| SEE Grow Limited | Professional & scientific | 2017 |
| Seebeck 164 Limited | Hospitality | 2019 |
| Seebeck 166 Limited | Real estate | 2001 |
| Seedlings Care Limited | Health & social care | 2021 |
| Seedstone B-Ig Limited | Real estate | 2025 |
| Seek Travels Ltd | Administrative & support | 2018 |
| Seemi Touch Ltd | Other services | 2025 |
| SEF Group Ltd | Real estate | 2025 |
| Sefu Miah Property Invesment Ltd | Real estate | 2025 |
| Segl Limited | Real estate | 2023 |
| Segtapos Ltd | Administrative & support | 2010 |
| Sehguh Investments Limited | Professional & scientific | 2016 |
| Sehmi Financial Solutions Limited | Financial services | 2021 |
| Seiman Sears Recruitment Ltd | Administrative & support | 2011 |
| Selan Limited | Other services | 2016 |
| Selby Dental Care Ltd | Health & social care | 2011 |
| Selby Original Ltd | Wholesale & retail | 2025 |
| Select Events Ltd | Hospitality | 2023 |
| Select to Cart Limited | Wholesale & retail | 2025 |
| Select Villages Limited | Hospitality | 2015 |
| Selectbrief Limited | Other services | 1994 |
| Self-Assured Occupational Health Consultancy Services Ltd | Health & social care | 2016 |
| Self-Published Limited | Information & communication | 2018 |
| Sell and Move Ltd | Real estate | 2021 |
| Sellindge West 10 Renewables Limited | Professional & scientific | 2023 |
| Sellitto Family Holdings Limited | Financial services | 2016 |
| SELO49 Ltd | Hospitality | 2024 |
| Selormey Accountancy Limited | Professional & scientific | 2026 |
| Selormey Holdings Limited | Financial services | 2026 |
| Selormey Limited | Information & communication | 2024 |
| Selva Fulfilment Limited | Transport & logistics | 2021 |
| Selva Logistics Limited | Manufacturing | 2014 |
| Semente Properties CIC | Administrative & support | 2023 |
| Semiko Limited | Hospitality | 2023 |
| Semilong Closing Company Limited | Health & social care | 2020 |
| Semilong Community Exchange Ltd | Health & social care | 2025 |
| Semilong Holdings Ltd | Financial services | 2023 |
| Semilong Mechanical Services Ltd | Wholesale & retail | 2023 |
| Semilong Property Ltd | Real estate | 2025 |
| Semilong Road Flat Management Company Ltd. | Real estate | 1989 |
| Semilong Services Limited | Construction | 2009 |
| Sempre Dritto Ltd | Transport & logistics | 2011 |
| Sempre SKI Limited | Arts & recreation | 2010 |
| SEN Bright Solutions Ltd | Construction | 2021 |
| SEN Talk Tags Ltd | Manufacturing | 2026 |
| Senator Northampton Limited | Households | 1988 |
| Send Logistics Ltd | Transport & logistics | 2017 |
| Senda Ltd | Wholesale & retail | 2025 |
| Sends 4 DAD CIC | Health & social care | 2026 |
| Sendsational Families CIC | Education | 2025 |
| Senla Limited | Hospitality | 2019 |
| Senoz Limited | Hospitality | 2019 |
| Sensational Care Provisions Ltd | Health & social care | 2023 |
| Sensational Care Services Limited | Public administration | 2025 |
| Sensationuk Ltd | Wholesale & retail | 2020 |
| Sense of Place Cornwall Ltd | Manufacturing | 2020 |
| Senshine TM C.I.C. | Education | 2024 |
| Sensitive Education Consultancy Limited | Administrative & support | 2009 |
| Sensory Prism Ltd | Health & social care | 2026 |
| Sensorygrid RRD Limited | Energy | 2021 |
| Sentinel Support Services Ltd | Administrative & support | 2020 |
| Senyad Limited | Arts & recreation | 2017 |
| Sera Solutions Limited | Professional & scientific | 2023 |
| Serabiz Group Limited | Wholesale & retail | 2026 |
| Seraph Advisory Limited | Professional & scientific | 2026 |
| Seratio Limited | Information & communication | 2015 |
| Serbumbata Ltd | Construction | 2021 |
| Seremed Healthcare Ltd | Administrative & support | 2018 |
| Serenade Entertainment Ltd | Arts & recreation | 2024 |
| Serendipity Brides Limited | Wholesale & retail | 2014 |
| Serene Art Maker Ltd | Wholesale & retail | 2023 |
| Serengeti Spirits Ltd | Manufacturing | 2020 |
| Serenity Cleans Ltd | Other services | 2016 |
| Serenity Community Homes Ltd | Hospitality | 2025 |