| West Street Land Management Ltd | Households | 2003 |
| Western AG Ltd | Wholesale & retail | 2020 |
| Western Commercial Properties Ltd | Real estate | 2015 |
| Westland Horticulture Limited | Manufacturing | 1993 |
| WH MCK Limited | Agriculture & fishing | 2011 |
| Whiteisland Nursery Limited | Agriculture & fishing | 2024 |
| Whiterox Ltd | Administrative & support | 2023 |
| Whittles Supermarket Limited | Extraterritorial | 2009 |
| William Sprott (Portadown) Limited | Extraterritorial | 2022 |
| Willow Agencies Limited | Professional & scientific | 2018 |
| Willow Drive Company Limited | Construction | 2020 |
| Willow Farm Holdings Ltd | Financial services | 2019 |
| Willowbank Limited | Health & social care | 1985 |
| Willowbank Organic Producers Ltd | Agriculture & fishing | 2004 |
| Willowmount Developments Ltd | Construction | 2016 |
| Willswheels Specialist Cars Ltd | Wholesale & retail | 2018 |
| WIN Bear Competitions Limited | Wholesale & retail | 2020 |
| Wincor Ltd | Professional & scientific | 2024 |
| Windmill Holdings Limited | Professional & scientific | 2007 |
| Windmill Integrated Primary School Limited | Education | 1988 |
| Wings N Things Limited | Wholesale & retail | 2018 |
| WM Door-Sets Ltd | Manufacturing | 2024 |
| WM Group N.I. Ltd | Real estate | 2019 |
| WM Transport N.I. Ltd | Transport & logistics | 2020 |
| Wolfhound Vehicles NI Ltd | Wholesale & retail | 2013 |
| Wonder Haus Limited | Wholesale & retail | 2026 |
| Woodhill Trading Limited | Professional & scientific | 2017 |
| Woodlab Distillery Limited | Manufacturing | 2017 |
| Woodmarque Architectural Joinery Ltd | Manufacturing | 1987 |
| Woodmarque Architectural Joinery ROI Ltd | Construction | 2018 |
| Woodmarque Holdings Ltd | Financial services | 2018 |
| Woodport NI Ltd | Wholesale & retail | 2026 |
| Wylie Civil Engineering Ltd | Construction | 2021 |
| Wylie Stonemasons Ltd | Construction | 2013 |
| Xactcon Ltd | Professional & scientific | 2016 |
| Xeinadin NI Limited | Professional & scientific | 2013 |
| Xicomexi Ltd | Wholesale & retail | 2024 |
| Xtreme Iron Gym Ltd | Arts & recreation | 2024 |
| XYZ Lifts Ltd | Administrative & support | 2026 |
| Y Baba Restaurant Ltd | Hospitality | 2021 |
| Yellow Comply Ltd | Information & communication | 2025 |
| Yellow Fort Ltd | Administrative & support | 2019 |
| Yerac (2023) Limited | Real estate | 2023 |
| Yoccii Ltd | Arts & recreation | 2025 |
| YOU Heard Ltd | Real estate | 2025 |
| Youngrich Ltd | Manufacturing | 2024 |
| YTO Enterprises Ltd | Wholesale & retail | 2025 |
| Zaestheticshop Ltd | Wholesale & retail | 2025 |
| Zarsco Property Limited | Extraterritorial | 2023 |
| Zega Support Organisation | Health & social care | 2022 |
| Zentrix Enterprises Ltd | Wholesale & retail | 2026 |
| Zilvinas Raginskas Limited | Extraterritorial | 2023 |
| ZIP4U Limited | Wholesale & retail | 2013 |
| ZMD Aesthetics Ltd. | Health & social care | 2019 |
| Zoom Air Supplies Limited | Wholesale & retail | 2006 |
| Zoom Mortgages Ltd | Professional & scientific | 2020 |
| Zquad Ltd | Wholesale & retail | 2025 |