| Security Deposits Limited | Mining & quarrying | 2006 |
| Security Design Ltd | Administrative & support | 2020 |
| Security Fence Consultancy Ltd | Construction | 2016 |
| Security Fencing Solutions Ltd | Construction | 2020 |
| Security Solutions (Yorkshire) Limited | Construction | 2015 |
| Sedaudio Ltd | Information & communication | 2023 |
| Sedbergh Fell Limited | Real estate | 2025 |
| Sedcode Ltd | Information & communication | 2021 |
| Sedgeman IT Consultancy Limited | Information & communication | 2019 |
| Sedgison Ltd | Hospitality | 2026 |
| Sedigel Limited | Manufacturing | 2012 |
| Sedlan Strategic Marketing Ltd | Professional & scientific | 2026 |
| Seeai Ltd. | Information & communication | 2019 |
| Seed Harmony CIC | Professional & scientific | 2024 |
| Seeder Solutions Limited | Wholesale & retail | 2026 |
| Seedia & Sons Ltd | Transport & logistics | 2018 |
| Seedling Support UK Limited | Administrative & support | 2024 |
| Seeds Consulting UK Limited | Information & communication | 2020 |
| Seeds Health & Wellbeing Ltd | Information & communication | 2018 |
| Seeds Healthcare Ltd | Administrative & support | 2020 |
| Seeds Property Ltd | Real estate | 2020 |
| Seed’S Property Investments Limited | Real estate | 2025 |
| Seefa Ltd | Arts & recreation | 2026 |
| Seefarer Ltd | Wholesale & retail | 2021 |
| Seek Living Limited | Wholesale & retail | 2020 |
| Seekars Digital Services Ltd | Information & communication | 2026 |
| Seelam Consultancy Ltd | Health & social care | 2013 |
| Seemore Holidays Limited | Extraterritorial | 1986 |
| Seeraa Ltd | Information & communication | 2025 |
| Seeratenterprises Limited | Wholesale & retail | 2025 |
| Seeratun Property Management Ltd | Households | 2016 |
| Seetha Investments Ltd | Hospitality | 2026 |
| Seff Fibre Limited | Manufacturing | 2017 |
| Seff Global Limited | Manufacturing | 2024 |
| Seff Holdings Limited | Manufacturing | 2024 |
| Segal Fitness Limited | Health & social care | 2022 |
| Segmedia Ltd | Administrative & support | 2025 |
| Segments Club Ltd | Information & communication | 2026 |
| Seguridad Ltd | Administrative & support | 2025 |
| Segway Events Limited | Administrative & support | 2010 |
| SEI Health Ltd | Health & social care | 2023 |
| SEL Engineering Realisations Limited | Manufacturing | 1992 |
| Sel's Houses Limited | Real estate | 2019 |
| Sela Properties Ltd | Real estate | 2025 |
| Selah Services Limited | Health & social care | 2015 |
| Selam Homes Ltd | Real estate | 2023 |
| Selby Carpet Depot Limited | Wholesale & retail | 2006 |
| Selby Engineering & Lifting Safety Limited | Manufacturing | 1995 |
| Selby Engineering & Lifting Services Limited | Extraterritorial | 2006 |
| Selby Family Group Ltd | Wholesale & retail | 2016 |
| Selby Foods Limited | Wholesale & retail | 2008 |
| Selby Foods Management Limited | Professional & scientific | 2011 |
| Selby Foods Trading LLP | | 2011 |
| Selby Pizzeria Ltd | Hospitality | 2024 |
| Selby Produce Limited | Extraterritorial | 2013 |
| Selby Road Tyres Ltd | Wholesale & retail | 2003 |
| Selby Specialist Cars Ltd | Wholesale & retail | 2010 |
| Selby Station Taxis Limited | Transport & logistics | 2023 |
| Selby Tvr,Sports and Classics Ltd | Wholesale & retail | 2009 |
| Select a S Limited | Real estate | 2003 |
| Select Accommodation Ltd | Real estate | 2016 |
| Select Branding Solutions Limited | Wholesale & retail | 2026 |
| Select Floors Limited | Wholesale & retail | 2004 |
| Select Group Security Limited | Administrative & support | 2024 |
| Select Healthy Mind Limited | Health & social care | 2017 |
| Select Hotel Ltd | Hospitality | 2018 |
| Select Interiors (Cheshire) Limited | Construction | 2001 |
| Select Products (Yorkshire) Limited | Construction | 2011 |
| Select Properties (Leeds) Ltd | Real estate | 2015 |
| Select Supply UK Ltd | Wholesale & retail | 2026 |
| Select Uniforms Ltd | Wholesale & retail | 1997 |
| Select Vehicle Sourcing Ltd | Wholesale & retail | 2021 |
| Selectany Limited | Construction | 1997 |
| Selective Clothing Ltd | Wholesale & retail | 2019 |
| Selectplan Limited | Construction | 1990 |
| Selectrical Services (Leeds) Limited | Construction | 2006 |
| Selera Ltd | Hospitality | 2022 |
| Self Discovery CBT Limited | Health & social care | 2019 |
| Self Leeds Ltd | Other services | 2023 |
| Selfimed Ltd | Wholesale & retail | 2022 |
| Selig Services Ltd | Professional & scientific | 2024 |
| Selkirk and Westmoreland Limited | Construction | 1995 |
| Selkirk Lettings Ltd | Real estate | 2017 |
| Sell ANY Car Yorkshire Limited | Wholesale & retail | 2026 |
| Sellars Commercial Plumbing & Heating Services Ltd | Construction | 2022 |
| Sellcom Pro Ltd | Transport & logistics | 2022 |
| Sellers Plant Hire Limited | Administrative & support | 2014 |
| Selliance Consulting Ltd | Professional & scientific | 2024 |
| Selly Oak Insurance Services Limited | Financial services | 1994 |
| Selma Social Care Ltd | Health & social care | 2022 |
| Selmm Ltd | Wholesale & retail | 2023 |
| Semantic Visions Limited | Information & communication | 2020 |
| Semco-Uk Group Limited | Construction | 2013 |
| Semiramis Genetics Limited | Professional & scientific | 2008 |
| Semmbabe Ltd | Wholesale & retail | 2022 |
| Semoh Care Ltd | Health & social care | 2015 |
| Semore Limited | Real estate | 1969 |
| Semper Deinceps Limited | Professional & scientific | 2015 |
| Semz Ltd | Transport & logistics | 2025 |
| SEN Control System Limited | Professional & scientific | 2021 |