| Shaun Jones Ltd | Transport & logistics | 2026 |
| SHE Speaks Social Ltd | Professional & scientific | 2025 |
| Sheila Rogers Limited | Administrative & support | 2007 |
| Sheridan Drive Property Management Limited | Extraterritorial | 2002 |
| Sherlock Street Birmingham Limited | Extraterritorial | 2019 |
| Sherwood Property & Resource Management Ltd | Real estate | 2024 |
| She’S SOO Saucy Ltd | Manufacturing | 2022 |
| Shorefront Developments Ltd | Construction | 2016 |
| Shot Belfast Ltd | Wholesale & retail | 2025 |
| Shot Blasting Services Ltd | Manufacturing | 2022 |
| Shout Blue Ltd | Wholesale & retail | 2022 |
| Si-Lwli Cymru Limited | Wholesale & retail | 2017 |
| SID Developments Limited | | 2006 |
| Sigma Wireless Communications Limited | | 1999 |
| Signature Leather Limited | Manufacturing | 2005 |
| Signature Windows NI Ltd | Construction | 2018 |
| Signs & Graphics (Bangor) Ltd | Professional & scientific | 2009 |
| Signs Workshop Limited | Manufacturing | 2004 |
| Silent Discovery Limited | Arts & recreation | 2020 |
| Silverstream Apartments Management Limited | Extraterritorial | 2005 |
| Silverstream Mews Management Company Ltd | Extraterritorial | 2005 |
| Simon Christie Consulting Ltd | Professional & scientific | 2024 |
| Simply Mobile (NI) Ltd. | Information & communication | 2010 |
| Singularis Education Limited | Education | 2013 |
| Sion Owens Roofing Limited | Construction | 2023 |
| Siop DEL Cyfyngedig | Wholesale & retail | 2023 |
| Siop Menai (Bangor) Ltd | Wholesale & retail | 2023 |
| Sitar Indian Takeway Ltd | Hospitality | 2024 |
| Site Safety Engineering Ltd | Professional & scientific | 2024 |
| SJ Conversions Limited | Wholesale & retail | 2015 |
| SJH Imaging Solutions Limited | Health & social care | 2026 |
| SJP Financial Solutions Ltd | Professional & scientific | 2022 |
| Sjpbookkeeping (NI) Limited | Professional & scientific | 2013 |
| SK Pharmasolutions Ltd | Wholesale & retail | 2022 |
| Skin Club Academy Ltd | Other services | 2024 |
| Skinn by Emma Davies Ltd | Other services | 2024 |
| Skirmshop Ireland Ltd | Manufacturing | 2021 |
| Skunder Limited | Information & communication | 2025 |
| Skyline Real Estate Limited | Real estate | 2013 |
| Skyloop Productions Ltd | Manufacturing | 2025 |
| Sling Limited | Real estate | 2003 |
| Slow Draw Ltd | Information & communication | 2015 |
| Smart Sustainability Ltd | Professional & scientific | 2023 |
| Smarterlight Ltd | Professional & scientific | 2011 |
| Smasher N.I Ltd | Hospitality | 2022 |
| Smoothie Factory Bangor Ltd | Wholesale & retail | 2022 |
| Smyth Research Limited | Manufacturing | 2007 |
| SNA Consulting Ltd | Hospitality | 2022 |
| Snowdon Leisure Ltd | Wholesale & retail | 2022 |
| Snowdon Ltd | Wholesale & retail | 2022 |
| Snowdon Timber Ltd | Wholesale & retail | 2020 |
| Snowdon Timber Products Ltd | Wholesale & retail | 2019 |
| Snowdonia Aviation Limited | Education | 2014 |
| Snowdonia Building Group Ltd | Construction | 2025 |
| Snowdonia Cottages Limited | Hospitality | 2017 |
| Snowdonia Hospitality and Leisure Limited | Hospitality | 1972 |
| Snowdonia Landscaping Limited | Administrative & support | 2023 |
| Snowdonia Mountain Lodge Ltd | Real estate | 1993 |
| Snowdonia Training Solutions Ltd | Education | 2021 |
| Snowdonia Walking and Climbing Ltd | Education | 2023 |
| Snuggles Day Nursery Ltd | Education | 2015 |
| SO Chic Bangor CYF | Wholesale & retail | 2013 |
| Soap Box Properties Ltd | Other services | 2013 |
| SOC Design Solutions Limited | Information & communication | 2015 |
| Social Fairy Limited | Financial services | 2024 |
| SOL Travel Ltd | Administrative & support | 2025 |
| Solar Rose Limited | Health & social care | 2023 |
| Solid Grey Ltd | Professional & scientific | 2021 |
| Solid Web Foundations Ltd | Information & communication | 2010 |
| Solutions for Systems Ltd | Construction | 2018 |
| Somnitect Limited | Wholesale & retail | 2025 |
| Sonas Ventures Ltd | Hospitality | 2019 |
| Sonic Academy Limited | Wholesale & retail | 2010 |
| Soren Academics Ltd | Other services | 2026 |
| Soultrane C.I.C. | Arts & recreation | 2023 |
| South Belfast Developments Limited | Construction | 2014 |
| South Stack Ynys Lawd Ltd. | Administrative & support | 2017 |
| Space & Space Limited | Hospitality | 2007 |
| SPAG33 Limited | Hospitality | 2024 |
| Sparkle Car Wash Belfast Ltd | Wholesale & retail | 2024 |
| Speciality Exam Limited | Professional & scientific | 2016 |
| Specifi.Io Ltd | Information & communication | 2021 |
| Speedy Screenprint Limited | | 1994 |
| Spence Furnishings Ltd | Manufacturing | 2023 |
| Spence Roofing Ltd | Construction | 2023 |
| Sperrin Forest Trails Limited | Real estate | 2016 |
| Sperrin View Property Management Ltd | Real estate | 2015 |
| Spiritbond Elephant & Castle Limited | Construction | 2013 |
| Spiritbond Finsbury Park Limited | Construction | 2009 |
| Spiritbond Stockwell Green Limited | Construction | 2010 |
| Sporeshore Mushrooms Ltd | Agriculture & fishing | 2020 |
| Sports & Social Media Limited | Wholesale & retail | 2013 |
| Sports Card Competitions Ltd | Arts & recreation | 2025 |
| Sports Crest Limited | Extraterritorial | 1998 |
| Spotless Horizon Ltd | Administrative & support | 2026 |
| Spotty Dog Computers Ltd | Wholesale & retail | 2015 |
| Square One Consultancy Ltd | Real estate | 2014 |
| Square One Realty Ltd | Real estate | 2016 |
| Square Step Ltd | Professional & scientific | 2022 |
| SRT Holdings Ltd | Wholesale & retail | 2017 |