| SMV Motors Ltd | Wholesale & retail | 2021 |
| SMW Technical Limited | Professional & scientific | 2023 |
| SNB Enterprises Ltd | Financial services | 2014 |
| SNG Capital Ltd | Real estate | 2015 |
| Sniblock Ecommerce Ltd | Wholesale & retail | 2023 |
| SO Homes 2025 Ltd | Construction | 2024 |
| SO Living Ltd | Financial services | 2024 |
| Social H Limited | Administrative & support | 2019 |
| Solarmix Ltd | Construction | 2026 |
| Somerton Limited | | 2004 |
| Soul Sauna 2025 Ltd | Other services | 2025 |
| Sound Light SET Ltd | Information & communication | 2025 |
| Source Creative Consulting Ltd | Professional & scientific | 2014 |
| South Antrim BIO Limited | Energy | 2011 |
| South Antrim Boiler Services Limited | Manufacturing | 1992 |
| South West Drainage Services Ireland Ltd | Water & waste | 2022 |
| Sovereign Security and Financial Ltd | Professional & scientific | 2001 |
| Space-Clean Ltd | Administrative & support | 2026 |
| SPE Contracts Ltd | Construction | 2006 |
| Spearhead Risk Consultancy Ltd | Administrative & support | 2014 |
| Specialist Finishing Group Ltd | Construction | 2017 |
| Speechtherapyni Limited | Health & social care | 2022 |
| Speed Motion Films Limited | Information & communication | 2013 |
| Speedlink (N. Ireland) Limited | Transport & logistics | 2009 |
| Speedlink Cargo Ltd | Transport & logistics | 2023 |
| SPI Trading Limited | Hospitality | 2013 |
| Spoil & Spa Ltd | Health & social care | 2020 |
| Sportsfix Limited | Information & communication | 2022 |
| Sprd Investments Limited | Real estate | 2013 |
| Spruce Hillsborough Limited | Financial services | 2022 |
| Spruce Meadows Ltd | Arts & recreation | 2012 |
| Spud Zone Ltd | Hospitality | 2026 |
| Sree Guru Holdings Ltd | Health & social care | 2017 |
| ST Ignatius Orthodox Church | Other services | 2010 |
| Stable Lane Limited | Extraterritorial | 2006 |
| Stadyume Ltd | Wholesale & retail | 2026 |
| Staffly Limited | Information & communication | 2024 |
| Stainless Metals and Alloys (2019) Limited | Wholesale & retail | 2018 |
| Stanzwil Properties Ltd | Real estate | 2024 |
| Starrett Joinery Ltd | Manufacturing | 2022 |
| Starsloeu Ltd | Wholesale & retail | 2026 |
| Start EV Charge Ltd | Construction | 2022 |
| Start Scaffolding Ltd | Construction | 2024 |
| Start Solar Ltd | Wholesale & retail | 2019 |
| Starwell Invest LLP | | 2014 |
| Stary Trade LLP | | 2015 |
| Steen's Ireland Limited | Administrative & support | 1973 |
| Stelor Distribution Limited | Wholesale & retail | 2015 |
| Stephen Hamill Golf Limited | Arts & recreation | 2014 |
| Stephen Mcelhinny Electrical Ltd | Construction | 2026 |
| Stephenson Safeguarding Consultancy Limited | Professional & scientific | 2026 |
| Stewart Martin Ltd | Wholesale & retail | 2017 |
| Stock-Right Company Limited | Agriculture & fishing | 1982 |
| Stone Dead Ltd | Professional & scientific | 2014 |
| Stonewood Investment Group Limited | Financial services | 2024 |
| Stoneyford Engineering Ltd | Manufacturing | 2007 |
| Stoneyford Plant Hire Ltd | Other services | 2011 |
| Stoneyford Truck Parts Ltd | Wholesale & retail | 2015 |
| Storeway Ltd | Transport & logistics | 2026 |
| Strade Fareast Limited | Wholesale & retail | 2026 |
| Straight SIX Property Ltd | Real estate | 2025 |
| Strangford Acquisition 1 Limited | Manufacturing | 2024 |
| Strangford Capital Ltd | Professional & scientific | 2022 |
| Strangford Rugby Holdings Limited | Arts & recreation | 2024 |
| Stranmillis Developments Limited | Real estate | 1999 |
| Strategic Consultancy Services Limited | Professional & scientific | 2019 |
| Strategic Equity Ventures LLP | | 2021 |
| Strategic Investment Partners LLP | | 2021 |
| Stratosyn Limited | Information & communication | 2025 |
| Stratum Services LP | | 2025 |
| Stream Motors Ltd | Wholesale & retail | 2014 |
| Streamlight Trade L.P. | | 2018 |
| Strive Innovation Ltd | Wholesale & retail | 2026 |
| Stroke B.O.Y Ltd | Wholesale & retail | 2024 |
| Structural Design & Detailing Limited | Professional & scientific | 2007 |
| Studio Glow BG Ltd | Other services | 2026 |
| Studioy Ltd | Professional & scientific | 2025 |
| Success@ Ltd | Wholesale & retail | 2025 |
| Sugar Art BT Ltd | Hospitality | 2026 |
| Suki Teahouse Limited | Manufacturing | 2005 |
| Sulaco NI Limited | Information & communication | 2016 |
| Suleman Catering (2016) Ltd | Hospitality | 2016 |
| Summer Garden Ltd | Manufacturing | 2017 |
| Sun Deals Limited | Manufacturing | 2024 |
| Sunflower DW Limited | Hospitality | 2006 |
| Sunlight Commerce LLP | | 2016 |
| Sunny's (2020) Ltd | Hospitality | 2020 |
| Sunny's (Magherafelt) Ltd | Hospitality | 2018 |
| Sunpartners Limited | Extraterritorial | 2014 |
| Sunrise Commerce LP | | 2019 |
| Sunroom Solutions (N.I.) Limited | Construction | 2018 |
| Superchip (NI) Limited | Wholesale & retail | 2011 |
| Supreme Financial Advisors Limited | Professional & scientific | 2020 |
| Supreme Shopfitting Limited | Construction | 2012 |
| Supremetechbusiness LP | | 2022 |
| Supwgone Ltd | Wholesale & retail | 2026 |
| Surefire Heating Ltd | Construction | 2022 |
| Sustainable Faith Global | Administrative & support | 2023 |
| Suzie LEE Cooks Limited | Hospitality | 2021 |
| SVR Medical Limited | Real estate | 2022 |