| SD Road Contracts Limited | Construction | 2011 |
| Sea Breath Limited | Manufacturing | 2025 |
| Sea Safety Consulting Ltd | Transport & logistics | 2018 |
| Seaforde Scrap Metals Limited | Wholesale & retail | 2011 |
| Seaforde Skip Hire Limited | Water & waste | 2011 |
| Seamus Fitzsimons Funeral Directors Limited | Other services | 2012 |
| Sean Fitzsimons Asset and Maintenance Management Consultant Limited | Professional & scientific | 2025 |
| Sebeneo Sports Solutions Ltd | Wholesale & retail | 2016 |
| Secure Trans Ltd | Transport & logistics | 2017 |
| Sentinel Network Solutions Ltd | Information & communication | 2025 |
| Seqo Ltd | Information & communication | 2023 |
| SH Operations Services Ltd | Construction | 2022 |
| Shairstock Ltd | Financial services | 2025 |
| Shift Control Ltd | Information & communication | 2007 |
| Shindig Arts Ltd | Administrative & support | 2022 |
| SIA Holdings Ltd | Real estate | 2019 |
| Siignal Recordings Ltd | Information & communication | 2023 |
| Simple Abode (N.I.) Ltd | Real estate | 2020 |
| Simsek Luxury Turkish Barbers Ltd | Other services | 2026 |
| SIR Hans Sloane Centre Ltd | Education | 2019 |
| Sirob Ltd | Construction | 2016 |
| Sistersin | Education | 2022 |
| Sky Charge Renewables Ltd | Construction | 2026 |
| Skyline Tree Surgery Ireland Limited | Agriculture & fishing | 2023 |
| Skyview Entertainment Limited | Wholesale & retail | 2017 |
| Slaney Park Enterprises Limited | Agriculture & fishing | 1998 |
| Slice Pizzeria Clough Ltd | Hospitality | 2024 |
| Slugger O'Toole Limited | Information & communication | 2008 |
| Slurryquip Ltd | Manufacturing | 2015 |
| SM8 Holdings Limited | Financial services | 2018 |
| Smart Blind Solutions Ltd | Wholesale & retail | 2021 |
| Smart Screen Ltd | Wholesale & retail | 2025 |
| Smart Systems (N.I.) Ltd | Professional & scientific | 2021 |
| Smiton Maintenance Limited | Manufacturing | 2017 |
| SND Joinery Limited | Construction | 2021 |
| Soaring Productions Ltd | Information & communication | 2025 |
| Soben International (Europe) Ltd | Wholesale & retail | 2006 |
| South Down Joinery & Building Services Ltd | Construction | 2020 |
| South Promenade Apartment Management (Newcastle) Limited | Households | 2021 |
| Spare Chair Ltd | Information & communication | 2024 |
| Specially Connected C.I.C. | Education | 2022 |
| Spectrum Distribution NI Ltd | Wholesale & retail | 2026 |
| Sportscape Ireland Limited | Construction | 2026 |
| Spreadpoint Ltd | Manufacturing | 2019 |
| Srad Properties Limited | Real estate | 2019 |
| SRF Ltd | Manufacturing | 2019 |
| Stable Innovations Ltd | Professional & scientific | 2018 |
| Stagemode Technologies Ltd | Information & communication | 2025 |
| Standupfor Limited | Wholesale & retail | 2025 |
| Stansoro Property Ltd | Real estate | 2023 |
| Station Park Killyleagh Management Company Limited | Households | 2019 |
| Steel CON (N.I.) Limited | Manufacturing | 2018 |
| Stella Maris Street Management Company Limited | Households | 2010 |
| Strangford Boat Excursions Limited | Administrative & support | 2025 |
| Strangford Community Association Developments Ltd | Arts & recreation | 2005 |
| Strangford Court Management Company Limited | Households | 2008 |
| Strangford Holiday Park Ltd | Hospitality | 2012 |
| Strangford Lough Brewing Company Limited | | 2004 |
| Strangford Lough Properties Limited | Construction | 2012 |
| Strangford Pictures Ltd | Arts & recreation | 2015 |
| Struell Contracts (NI) Ltd. | Construction | 2019 |
| Struell Ltd | Construction | 1978 |
| Struell Oakley Holdings Ltd | Hospitality | 2025 |
| Sunrise Film Productions Ltd | Information & communication | 2022 |
| Supersavers Opticians Limited | Wholesale & retail | 2004 |
| Swift Fuels Limited | Wholesale & retail | 2018 |
| Swift Security 365 Ltd | Administrative & support | 2020 |
| Swisstrans Ltd. | Transport & logistics | 2018 |
| T Wills & Sons (NI) Limited | Agriculture & fishing | 2012 |
| T Wills & Sons Limited | Agriculture & fishing | 2007 |
| T.T. Properties Limited | Real estate | 2013 |
| T4 Nails Ltd | Other services | 2024 |
| Taboo Retail Limited | Wholesale & retail | 2021 |
| Tacos & Cerveza Ltd | Hospitality | 2025 |
| Tarbot Media Ltd | Information & communication | 2025 |
| Tas-Ni Ltd | Education | 2020 |
| TCC Group Holdings Ltd | Financial services | 2026 |
| Teach Abroad Careers Ltd | Administrative & support | 2023 |
| TEC Eleven Holdings Ltd | Financial services | 2023 |
| Technical and Business Solutions Limited | Information & communication | 2015 |
| Teller Films (UK) Ltd | Information & communication | 2024 |
| Test (NI) Ltd | Professional & scientific | 2014 |
| Texas Star Pizza Ltd | Hospitality | 2018 |
| THE Aesthetic Collective Ltd | Administrative & support | 2025 |
| THE Artisan Cookhouse Ltd | Hospitality | 2025 |
| THE Cabin Tea Rooms & Farm Shop Ltd | Wholesale & retail | 2025 |
| THE Chefs Mill Ltd | Hospitality | 2021 |
| THE Finnebrogue Bacon Company Ltd | Manufacturing | 2017 |
| THE Firs (One) Apartment Management Limited | Households | 2025 |
| THE Firs (Two) Apartment Management Company Limited | Households | 2025 |
| THE Firs Management (Holywood) Company Limited | Households | 2025 |
| THE Good Smoked Cheese Company Ltd | Manufacturing | 2024 |
| THE Greenest Gift Company Ltd | Extraterritorial | 2024 |
| THE Gymnastics and Trampoline Network C.I.C. | Arts & recreation | 2020 |
| THE Linen Distillery Ltd | Manufacturing | 2024 |
| THE Magnificent Seven Trading Company Limited | Wholesale & retail | 2014 |
| THE River Quoile Trust | Professional & scientific | 2023 |
| THE Rock Hollow Resort Ltd | Hospitality | 2025 |
| Thinkbridge Consulting Ltd | Professional & scientific | 2023 |
| Thirst Trap Water Company Ltd | Manufacturing | 2023 |