| Samaritans of Omagh | Other services | 2017 |
| Sanctuary Security Services Ltd | Administrative & support | 2024 |
| Sandstone Capital Investments | Real estate | 2026 |
| Sandyhill Place Management Company Limited | Households | 2020 |
| Saol Longevity Ltd | Health & social care | 2026 |
| SAP Trading (Omagh) Ltd | Other services | 2024 |
| Sari Sari the Filipino Asian Store Ltd | Wholesale & retail | 2022 |
| Sawel Contracts Ltd | Construction | 2022 |
| SB Hseq Limited | Construction | 2019 |
| SB Tyres Ltd | Wholesale & retail | 2022 |
| Sbaap Holdings Ltd | Financial services | 2023 |
| Sbs(Ni) Limited | Arts & recreation | 2023 |
| SC Concrete and Formwork Ltd | Construction | 2025 |
| SC Pave Limited | Construction | 2013 |
| Sc&P Civils Limited | Construction | 2017 |
| Sc&P Contracts Limited | Construction | 2014 |
| Scalp View Farms Ltd | Agriculture & fishing | 2014 |
| Scalph Wind Energy Ltd | Energy | 2015 |
| Scarpa Northwest Ltd | Wholesale & retail | 2012 |
| Schimmel Distribution Limited | Financial services | 2023 |
| Scissor Sisters Belfast Ltd | Other services | 2017 |
| Scott & Ewing (Holdings) Limited | Extraterritorial | 2013 |
| Scott & Ewing Limited | Construction | 1974 |
| Scéalaí Productions Limited | Information & communication | 2019 |
| SD Cars Ltd | Wholesale & retail | 2023 |
| SD Electrical Contracts Ltd | Construction | 2017 |
| SD Engineering (NI) Ltd | Manufacturing | 2011 |
| SD Procurement Ltd | Wholesale & retail | 2025 |
| Sealo Holdings Ltd | Real estate | 2024 |
| Seamus Grogan Ltd | Mining & quarrying | 2023 |
| Sean Donnelly Construction Limited | Construction | 2018 |
| Sean&Kathleen Kerr Ltd | Agriculture & fishing | 2012 |
| Sedan Investments Limited | Real estate | 2020 |
| Segully Energy Limited | Energy | 2023 |
| Segully Holdings Ltd | Financial services | 2025 |
| Serelex Ltd | Professional & scientific | 2026 |
| Serenity Bathrooms Ltd | Manufacturing | 2024 |
| Seskinore 2 Limited | Construction | 2025 |
| Seskinore Dairy Farmers' Buying Group Ltd | Agriculture & fishing | 2013 |
| Seskinore Poultry Farm Ltd | Agriculture & fishing | 2020 |
| SET2LET Ltd | Real estate | 2024 |
| SG Couriers Ltd | Transport & logistics | 2022 |
| SH Behavioural Consultant Ltd | Education | 2025 |
| Shandun Industrial Services Ltd | Construction | 2015 |
| Shanmullagh Poultry Ltd | Agriculture & fishing | 2011 |
| Shark Tank Training Ltd | Arts & recreation | 2022 |
| Sharkey Bathrooms Ltd | Wholesale & retail | 2020 |
| Sharpur Consultancy Ltd | Professional & scientific | 2023 |
| Sharpur Property Ltd | Real estate | 2026 |
| Shauna Blair Ltd | Professional & scientific | 2024 |
| Shean Mushrooms Ltd | Agriculture & fishing | 2020 |
| Sheerin Fencing & Groundworks Ltd | Construction | 2024 |
| Shergrim Recycling Limited | Water & waste | 2004 |
| Sherlock Homes Developments Group Ltd | Construction | 2024 |
| Shire Enterprises Ltd | Financial services | 2012 |
| SHM Veterinary Services Ltd | Professional & scientific | 2020 |
| Shortt Livestock Haulage Ltd | Transport & logistics | 2018 |
| Shyvana Ltd | Wholesale & retail | 2026 |
| SI Wind Ltd | Energy | 2014 |
| Signal Print Ltd | Manufacturing | 2025 |
| Signal Signs (Omagh) Ltd | Professional & scientific | 2017 |
| Signature Event Catering Ltd | Hospitality | 2017 |
| Silverbrook Mill Ltd | Arts & recreation | 1994 |
| Silverline Competitions Ltd | Arts & recreation | 2025 |
| Simple Asset Finance Limited | Wholesale & retail | 2011 |
| Simplipayroll Ltd | Professional & scientific | 2011 |
| Simply Beauty Ltd | Other services | 2020 |
| Simpro Ireland Ltd | Agriculture & fishing | 2001 |
| Sine Anois Limited | Construction | 2024 |
| Sion Hydro Limited | Energy | 2012 |
| Siopa Achadh Leathan | Wholesale & retail | 2026 |
| Sisco (N.I.) Ltd | Manufacturing | 2015 |
| Sitas Developments UK Limited | Construction | 2012 |
| Site Services (NI) Limited | Construction | 2005 |
| Sitetainer Ltd | Manufacturing | 2026 |
| SIX PIG Network Ltd | Information & communication | 2021 |
| SJB Beauty Ltd | Other services | 2024 |
| SJM Motors (NI) Ltd | Wholesale & retail | 2011 |
| SK Engineering (NI) Ltd | Manufacturing | 2012 |
| Skin Aesthetics (N.I.) Ltd | Other services | 2024 |
| Skinpharm Aesthetic Solutions Ltd | Health & social care | 2022 |
| SL Motor Events Ltd | Administrative & support | 2025 |
| SL Wheels Ltd | Wholesale & retail | 2026 |
| Slack Panda Productions Ltd | Information & communication | 2023 |
| Slane Building Contracts Limited | Construction | 2018 |
| Sleeping Paws Ltd | Water & waste | 2025 |
| SLG Road Safety (NI) Limited | Construction | 2019 |
| Slievebeg Ltd | Construction | 2017 |
| Slievemore Limited | Agriculture & fishing | 2020 |
| Sluggan Stables Limited | Agriculture & fishing | 2022 |
| SM & SON Contracts Ltd | Agriculture & fishing | 2024 |
| SM & SON Engineering Ltd | Manufacturing | 2019 |
| SM Contracts (Dromore) Ltd | Transport & logistics | 2020 |
| SM Electrical Contracts Limited | Construction | 2024 |
| SM Retail Sales Ltd | Wholesale & retail | 2025 |
| SM Surfacing Limited | Construction | 2022 |
| SMB Electrics Ltd | Construction | 2007 |
| SMC Drywall Ltd | Construction | 2018 |
| SMC Groundworks Ltd | Construction | 2013 |
| SMC Neuropsychology Consulting Ltd | Health & social care | 2017 |