| Simplyfruit (UK) Limited | Wholesale & retail | 2007 |
| Sink the INK Limited | Wholesale & retail | 2016 |
| Sionnach Consulting Ltd | Information & communication | 2014 |
| Sirroni Ltd | Wholesale & retail | 2021 |
| SJ Anderson Properties Ltd | Real estate | 2024 |
| SJ Titan Storage Ltd | Administrative & support | 2026 |
| SJC Agencies Ltd | Wholesale & retail | 2018 |
| SJK CA Ltd | Professional & scientific | 2021 |
| Sjlm Limited | Real estate | 2011 |
| SJR Building Services Ltd | Construction | 2022 |
| SKD Building and Paving Limited | Construction | 2026 |
| SKD Gym Ltd | Arts & recreation | 2023 |
| Skinny's Pizza and Kebab House Ltd | Hospitality | 2025 |
| Sky Watch NI | Administrative & support | 2020 |
| Skye Fitness Limited | Arts & recreation | 2015 |
| Slade Developments Limited | Agriculture & fishing | 2004 |
| Slane Investors Ltd | Real estate | 2022 |
| SLK Khattak Ltd | Hospitality | 2026 |
| SLK Limited | Administrative & support | 2025 |
| Slmk Limited | Hospitality | 2003 |
| Slms 2020 Limited | Wholesale & retail | 2019 |
| Sloan Street Stores Ltd | Wholesale & retail | 2023 |
| SM Global Properties Ltd | Real estate | 2025 |
| Smart Hand Car Wash Ltd | Other services | 2021 |
| Smashing Times Theatre Company | Other services | 2009 |
| SMC Accountants Ltd | Professional & scientific | 1997 |
| SMD Accounting Ltd | Professional & scientific | 2024 |
| SME Business Support Ltd | Administrative & support | 2022 |
| Smoke Wizards NI Ltd. | Transport & logistics | 2021 |
| Smycon Homes Limited | Construction | 2017 |
| Smyth Building Services Limited | Construction | 2013 |
| Smyth Window Systems Limited | Construction | 2014 |
| Snagabuild Ltd | Other services | 2021 |
| SO Nice Ice Cream Ltd | Hospitality | 2024 |
| SOC Brickwork Ltd | Construction | 2026 |
| Sockped Limited | Professional & scientific | 2013 |
| SOH Construction Forces Ltd | Construction | 2025 |
| SOH Food Ltd | Hospitality | 2020 |
| Soho Fashion NI Ltd | Wholesale & retail | 2017 |
| Soho Fast Fashions Limited | Wholesale & retail | 2024 |
| Soho NI Properties Ltd | Real estate | 2018 |
| Solagbade Life Services Limited | Health & social care | 2024 |
| Solar Panels Green Energy Limited | Construction | 2021 |
| Solas Teas Ltd | Manufacturing | 2025 |
| Solitude Consulting Ltd | Information & communication | 2020 |
| Solitude Properties Ltd | Real estate | 2021 |
| Solomon Generation (UK) Limited | Financial services | 2012 |
| Solutions Transport Limited | Transport & logistics | 2021 |
| Solv Invest Ltd | Real estate | 2024 |
| Solve Property Investments Ltd | Real estate | 2025 |
| Soul Catalyst Films Ltd | Information & communication | 2022 |
| Sound Connect Studios Ltd | Information & communication | 2021 |
| Soundbox Consulting Limited | Administrative & support | 2016 |
| South Antrim Developments LLP | | 2006 |
| South Antrim Properties Ltd | Real estate | 2024 |
| South Antrim Services Limited | Real estate | 2016 |
| South Shore Power (Ireland) Ltd | Wholesale & retail | 2025 |
| SOX & JOX Ltd | Wholesale & retail | 2026 |
| Sparkys Autos Ltd | Wholesale & retail | 2025 |
| Sparta-Air Limited | Other services | 2017 |
| Specialist Estates Services Ltd | Professional & scientific | 2016 |
| Specialist Lake Services Ltd | Administrative & support | 2011 |
| Spectrum Advice Group Ltd | Financial services | 2023 |
| Spectrum Asset Protection Ltd | Administrative & support | 2007 |
| Spectrum Financial Planning Ltd | Financial services | 2024 |
| Spectrum Mortgages & Protection Ltd | Financial services | 2017 |
| Spectrum Wealth Management Ltd | Financial services | 2016 |
| Speedi Rentals Ltd | Administrative & support | 2022 |
| Spence Bryson Holdings Limited | Financial services | 2018 |
| Spence Bryson Limited | Manufacturing | 2002 |
| Spice House Lurgan Ltd | Hospitality | 2023 |
| Spin Haven Ltd | Other services | 2025 |
| Spinners Court Management Limited | Households | 2014 |
| Sports City Limited | Education | 2022 |
| Springfield Court Management Co. Ltd | Households | 2002 |
| Springhill Springs Ltd | Manufacturing | 2024 |
| Springvale Holding Company Limited | Financial services | 2018 |
| Spruced UP Property Services Ltd | Construction | 2026 |
| SQ Bricklaying Ltd | Construction | 2020 |
| Squint Creative Ltd | Arts & recreation | 2020 |
| SSS Alleviate Ltd | Construction | 2022 |
| ST Annes (Lurgan) Management Limited | Households | 2022 |
| ST Ronan's College Foundation | Education | 2021 |
| Stanley Emerson & Sons Limited | Mining & quarrying | 1979 |
| Star Kitchen Wang Ltd | Hospitality | 2023 |
| Star Properties (NI) Ltd | Real estate | 2012 |
| Starni C.I.C. | Health & social care | 2021 |
| Statement Groom Ltd | Wholesale & retail | 2018 |
| Station 231 Ltd | Information & communication | 2020 |
| Staycold NI Limited | Extraterritorial | 2020 |
| Stayinn Ltd | Hospitality | 2025 |
| STB Developments Ltd | Real estate | 2024 |
| Steel Detailing NI Limited | Professional & scientific | 2022 |
| Stem BSG Ltd | Manufacturing | 2022 |
| Stephen Budde Consulting Ltd | Professional & scientific | 2019 |
| Stephen Shanks Strength and Conditioning Limited | Arts & recreation | 2024 |
| Stepping Stone Properties Ltd | Construction | 2010 |
| Stevenson & Cumming (Portadown) Ltd | Real estate | 2010 |
| Stewart's Flooring Ltd | Construction | 2026 |
| Stonebarn Stables Ltd | Hospitality | 2024 |