| SSB Bangor Ltd | Wholesale & retail | 2024 |
| ST Clements Court Owners Management Ltd | Real estate | 2014 |
| ST. Gerard's School Trust | Education | 1990 |
| ST. Marks Apartments Management NO. 1 Limited | Extraterritorial | 2006 |
| ST. Marks Apartments Management NO.2 Limited | Extraterritorial | 2006 |
| ST. Marks Apartments Management NO.3 Limited | Extraterritorial | 2007 |
| Stables Limited - the | Extraterritorial | 1986 |
| Stand OUT Exhibitions and Display Ltd | Manufacturing | 2022 |
| Stanley & Longfellow Limited | Real estate | 2025 |
| Stapehill Investment Co. Limited | Administrative & support | 2012 |
| Star Properties and Maintenance Ltd | Real estate | 2024 |
| Starr Removals Ltd | Transport & logistics | 2022 |
| Station Walk Bangor Management Company Limited | Extraterritorial | 2012 |
| Steliman Limited | Other services | 2024 |
| Stephen Johnston Consulting Ltd | Professional & scientific | 2025 |
| Stephen Jones Funeral Directors Ltd. | Other services | 2017 |
| Sterling Wales Limited | Real estate | 2003 |
| Sterna Environmental Limited | Professional & scientific | 2014 |
| Stewart Estates (N.I.) Limited | Real estate | 1964 |
| Stirling Tuition Ltd | Education | 2017 |
| Stoke City Catering Limited | Hospitality | 2025 |
| Stonebridge People Solutions Limited | Professional & scientific | 2023 |
| Stonebrooke Kitchens Limited | Wholesale & retail | 2009 |
| Stoneharry Ltd | Real estate | 2023 |
| Stop and Shop (Bangor) Ltd | Wholesale & retail | 2015 |
| Store 127 Limited | Hospitality | 2018 |
| STORE14 Ltd | Manufacturing | 2024 |
| STORE220 Ltd | Hospitality | 2019 |
| STORE97 Ltd | Real estate | 2024 |
| Storehouse North Down | Other services | 2015 |
| Storfa Bocs CYF | Administrative & support | 2025 |
| Stormalong Ltd | Administrative & support | 2026 |
| Stormcassie Cavaliers Limited | Agriculture & fishing | 2026 |
| Stove Stores Limited | Wholesale & retail | 2026 |
| Stoves & Co (N.I.) Ltd | Wholesale & retail | 2016 |
| Straits View Limited | Real estate | 2021 |
| Straken Foods Ltd | Hospitality | 2018 |
| Streborts Limited | Real estate | 2021 |
| Strides Day Opportunities Trust Limited | Health & social care | 2026 |
| Strobeedm CYF | Manufacturing | 2024 |
| Structur Property Solutions Ltd | Hospitality | 2023 |
| STS Consultancy Limited | Professional & scientific | 2005 |
| Stuart Flynn Electrical Ltd | Information & communication | 2014 |
| Studio 6 Management Company Limited | Households | 2018 |
| Stylegood Limited | Construction | 2007 |
| SU Safety Ltd | Administrative & support | 2018 |
| Sub-Culture Productions Limited | Information & communication | 2010 |
| SUB75 Ltd | Hospitality | 2024 |
| SUB76 Ltd | Hospitality | 2026 |
| Submar Salvage 2019 Limited | Other services | 2019 |
| Sudor Wellness Ltd | Other services | 2023 |
| Summerfield House Limited | Real estate | 2003 |
| Sunflower Sandwich Bar Limited | Hospitality | 2006 |
| Sunkissed Tanning Ltd | Other services | 2025 |
| Sunningdale Apartments Limited | Households | 1981 |
| Sunny TAI Rentals Ltd | Real estate | 2026 |
| Sunnyside Cottages Management Company Ltd | Real estate | 2020 |
| Super Dog Limited | Hospitality | 2020 |
| Superior Short Stays Limited | Hospitality | 2012 |
| Superior Short Stays Management Limited | Real estate | 2022 |
| Superscheme Limited | Construction | 2007 |
| Supreme Plumbing & Heating Solutions Ltd | Construction | 2025 |
| Surfacing Experts Ltd | Administrative & support | 2012 |
| Surflines Ltd | Wholesale & retail | 2003 |
| Surriento Limited | Hospitality | 2026 |
| Sutton Court Road Limited | Construction | 2017 |
| SVI Digital Systems Limited | Construction | 2021 |
| SVI Media Ltd | Construction | 2021 |
| Swan 9 Ltd | Hospitality | 2024 |
| Sweesi's Limited | Professional & scientific | 2016 |
| Sweetcheeks Productions Limited | Information & communication | 2025 |
| Swift Contractors Ltd | Manufacturing | 2025 |
| Swift Outside Foods Ltd | Hospitality | 2017 |
| Swift Rope Access Ltd | Manufacturing | 2022 |
| Swiftmatch Limited | Real estate | 2010 |
| Swim Ulster Limited | Arts & recreation | 2005 |
| Swinley Bay Ltd | Construction | 2020 |
| SWN Y Wylan Developments Limited | Real estate | 2007 |
| Swni Limited | Transport & logistics | 2024 |
| Swooper Rigging Ltd | Manufacturing | 2019 |
| Swswales Limited | Water & waste | 2014 |
| Sycamore Films Ltd | Information & communication | 2026 |
| Sylw CYF | Information & communication | 2015 |
| Syndicate Event Productions & Hire Ltd | Wholesale & retail | 2023 |
| Syndicate Lofts Limited | Information & communication | 1999 |
| Synergy Yachting Limited | Administrative & support | 2007 |
| Sysada Limited | Information & communication | 2013 |
| Szkcreative Ltd | Other services | 2022 |
| T R Cooke Ltd | Information & communication | 2025 |
| T T Roberts & SON Ltd | Construction | 2003 |
| T&L Luxury Accommodation and Cars Ltd | Hospitality | 2025 |
| T'S Removals and Storage Ltd | Transport & logistics | 2025 |
| T-Bolt Security Limited | Information & communication | 2022 |
| T.R.S. Promotions Ltd | Arts & recreation | 2023 |
| Tacsi PG Cars Ltd | Transport & logistics | 2026 |
| Tacsi Twix CYF | Transport & logistics | 2020 |
| Tactical Screen Training NI Ltd | Information & communication | 2025 |
| Tafarn Penllan White Horse Inn CYF | Hospitality | 2025 |
| Tag-Air Limited | Construction | 1988 |
| TAI Williams Ltd | Hospitality | 2020 |