| Seedgreen | Financial services | 2022 |
| Seedkeep Ltd | Real estate | 2021 |
| Seedlings of SEN Ltd | Agriculture & fishing | 2023 |
| Seesuu Ltd | Health & social care | 2023 |
| SEF Business Consultancy Ltd | Professional & scientific | 2024 |
| Segrat Limited | Health & social care | 2012 |
| Seisarl Properties Ltd | Hospitality | 2024 |
| Selby Bolt and NUT Ltd | Wholesale & retail | 2015 |
| Selby Stone Limited | Manufacturing | 2004 |
| Selcom Systems Limited | Information & communication | 1998 |
| Select Beauty Salon Ltd | Other services | 2010 |
| Select Security Systems (UK) Limited | Administrative & support | 2008 |
| Select Travel Portfolio Ltd | Administrative & support | 2011 |
| Selected Records Ltd | Wholesale & retail | 2025 |
| Self Help CBT Hub Limited | Information & communication | 2025 |
| Self Love Coaching Limited | Health & social care | 2023 |
| Self Love Studios Limited | Arts & recreation | 2020 |
| Seljon Limited | Real estate | 2021 |
| Sell Your Vintage Ltd | Wholesale & retail | 2025 |
| Sellers Group Ltd | Health & social care | 2022 |
| Sellmor Farming Limited | Agriculture & fishing | 2010 |
| Sellmor Property Limited | Real estate | 2020 |
| Sels Consulting Limited | Information & communication | 2019 |
| Selva Auto Services Ltd | Other services | 2021 |
| Selvans Ltd | Health & social care | 2022 |
| Semasi Foods Ltd | Hospitality | 2024 |
| Semiconductor Specialists Limited | Professional & scientific | 2000 |
| Semitec Solutions Limited | Professional & scientific | 2019 |
| Sen-Forward Ltd | Wholesale & retail | 2025 |
| Senator Homes Limited | Construction | 2001 |
| Senator Security Services Limited | Administrative & support | 1997 |
| Senga Holdings Limited | Administrative & support | 2022 |
| Senlac Property Management (HEE) Limited | Real estate | 2015 |
| Senlac Property Management (HLE) Limited | Real estate | 2015 |
| Sensitive Logistics Limited | Transport & logistics | 2022 |
| Sensory Active Limited | Education | 2010 |
| Senthan Ltd | Wholesale & retail | 2025 |
| Sentient Creative Limited | Information & communication | 2018 |
| Sentinel Ocean Systems Ltd | Manufacturing | 2021 |
| Sentr Ltd | Information & communication | 2021 |
| Senyap Transport Limited | Transport & logistics | 1998 |
| SEO Management Solutions Ltd | Professional & scientific | 2024 |
| SEP Design Ltd | Professional & scientific | 2022 |
| SEP Geo-Tech Ltd | Professional & scientific | 2021 |
| SEP Rail Engineering (Holdings) Ltd | Professional & scientific | 2020 |
| Sequoia Developments Limited | Professional & scientific | 1959 |
| Serena Management Ltd | Real estate | 2024 |
| Serendib Holdings Ltd | Wholesale & retail | 2023 |
| Serendipity York Limited | Health & social care | 2018 |
| Serenity in Leadership Ltd | Professional & scientific | 2017 |
| Sert Consulting Limited | Professional & scientific | 2021 |
| Services ALM Ltd | Construction | 2022 |
| Servpro Programmable Logic Controllers Limited | Manufacturing | 2004 |
| Sesame Bankhall Group Limited | Professional & scientific | 1998 |
| Sesame Bankhall Valuation Services Limited | Financial services | 2001 |
| Sesame General Insurance Services Limited | Financial services | 1985 |
| Sesame Limited | Administrative & support | 1993 |
| Sesame Services Limited | Administrative & support | 1989 |
| Sessions & Co. Ltd | Wholesale & retail | 2016 |
| Sessions York Ltd | Wholesale & retail | 2015 |
| SET Management Ltd | Professional & scientific | 2025 |
| Set&Scenic Limited | Construction | 2015 |
| Sevca Limited | Hospitality | 2023 |
| Seveer Limited | Financial services | 2019 |
| Seven Crown Group Ltd | Financial services | 2026 |
| Seven Hills Property Builders Limited | Construction | 2020 |
| Seven Pines Dental Limited | Health & social care | 2023 |
| Seven SIX Four Taxis Ltd | Transport & logistics | 2012 |
| Seven Spices (Leeds) Ltd | Hospitality | 2023 |
| Seven Two Consulting Ltd. | Professional & scientific | 2021 |
| Sevensight Group Limited | Wholesale & retail | 2020 |
| Seventeen-Twentyone Ltd | Wholesale & retail | 2023 |
| Severn Plus Enterprises Ltd | Agriculture & fishing | 2018 |
| Severn Veterinary Centre Limited | Extraterritorial | 2011 |
| Severnbrook Homes Limited | Extraterritorial | 1990 |
| SEW N SEW York Limited | Other services | 2017 |
| Seward Grass Machinery Limited | Real estate | 1986 |
| SEZ Apartments 1 Limited | Real estate | 2024 |
| SEZ Developments Limited | Real estate | 2019 |
| SFC Plus Shawarma Ltd | Hospitality | 2026 |
| SFC York Ltd | Hospitality | 2025 |
| SFH Consulting Ltd | Information & communication | 2023 |
| SFL Property Investment Limited | Construction | 2025 |
| SFW360 Ltd | Professional & scientific | 2020 |
| SG Office Solutions Limited | Real estate | 2025 |
| SG Pension Trustee Limited | Other services | 1961 |
| SG Storage Limited | Real estate | 2023 |
| SGB Construction (York) Ltd | Construction | 2003 |
| SGB Developments (York) Ltd | Construction | 2021 |
| SGM Heating & Plumbing Ltd | Construction | 2023 |
| SGR Construction Group Ltd | Construction | 2024 |
| SGS Property Rentals Ltd | Real estate | 2022 |
| SGT York Ltd | Hospitality | 2025 |
| SH Developments Limited | Real estate | 2021 |
| SH Rail Development Limited | Transport & logistics | 2025 |
| SH100 Ltd | Hospitality | 2022 |
| SH2 Ventures Limited | Professional & scientific | 2024 |
| Shabby to Chic York Ltd | Other services | 2023 |
| Shackleton Morris Limited | Professional & scientific | 2017 |
| Shadow Media Productions Limited | Information & communication | 2010 |