| J.P.G Financial (N.I.) Limited | Financial services | 2018 |
| JA Millar Retail Group Limited | Wholesale & retail | 2020 |
| Jabai Ltd | Information & communication | 2025 |
| Jacaranda International Limited | Information & communication | 2014 |
| Jackpot Bingo and Slots Ltd | Arts & recreation | 2015 |
| Jackson Auto Repairs Ltd | Wholesale & retail | 2018 |
| Jacob Gastro Consults Ltd | Health & social care | 2016 |
| Jadair Holdings Ltd | Financial services | 2023 |
| Jade Sea Route Limited | Wholesale & retail | 2025 |
| Jadepous Ltd | Wholesale & retail | 2026 |
| Jaffa Productions Limited | Information & communication | 2012 |
| JAM Tomorrow Holdings Ltd | Financial services | 2021 |
| James Black Restorations Limited | Wholesale & retail | 2010 |
| James Cunningham Ltd | Wholesale & retail | 2025 |
| James Haughey & Co Ltd | Construction | 2012 |
| James Leckey Design Limited | Manufacturing | 1989 |
| James Shaw Limited | Professional & scientific | 2008 |
| James Steele Landscapes Limited | Real estate | 2011 |
| Jamison Design Studio Ltd | Professional & scientific | 2025 |
| Jane Wray Design Ltd | Professional & scientific | 2015 |
| Jannat Damas Food Store and Café Limited | Hospitality | 2025 |
| Jans Developments Limited | Real estate | 2017 |
| Jans Investments Limited | Administrative & support | 2010 |
| Jans Leisure Group Limited | Hospitality | 2024 |
| Jansen & Kinsley Ltd | Professional & scientific | 2022 |
| Jape Properties Limited | Real estate | 2012 |
| Jawa Pubs Limited | Hospitality | 2023 |
| Jazare Limited | Real estate | 2014 |
| JB (Belfast) Limited | Wholesale & retail | 2023 |
| JB Carryduff Ltd | Wholesale & retail | 2020 |
| JB Rigging and Lifting Limited | Construction | 2019 |
| JBA Cricket Company LLP | | 2026 |
| JC Contract Services Ltd | Construction | 2016 |
| JC Contractors(Ni) Ltd | Construction | 2022 |
| JC Offshore Operations Ltd | Professional & scientific | 2020 |
| Jcfi Limited | Manufacturing | 2019 |
| JD Speaking and Strategy Limited | Education | 2018 |
| JDS Medical Services Ltd | Health & social care | 2021 |
| JE Signalling Ltd | Construction | 2024 |
| Jebb Holdings Limited | Extraterritorial | 2007 |
| Jeffrey & Adeline Williamson Ltd | Wholesale & retail | 2014 |
| Jelliebean Properties Limited | Real estate | 2017 |
| Jesse Blinds & Shutters Ltd | Manufacturing | 1995 |
| Jets Properties Ltd | Real estate | 2013 |
| JGH Gym Ltd | Other services | 2024 |
| JH & Co Accountants Limited | Professional & scientific | 2017 |
| JH1 Topco Limited | Financial services | 2024 |
| JIM Mcrandle Agencies Limited | Wholesale & retail | 2015 |
| Jim's DIY Ltd | Wholesale & retail | 2021 |
| Jipco Ltd | Real estate | 2008 |
| Jirunliu Ltd | Wholesale & retail | 2024 |
| Jj&A Enterprise Ltd | Financial services | 2024 |
| Jj&A Photo Ltd | Professional & scientific | 2024 |
| Jkcr Group Ltd. | Other services | 2017 |
| JKG Properties Limited | Construction | 2005 |
| JKS Inclusion Ltd | Education | 2023 |
| JL Protection Ltd | Financial services | 2022 |
| JLE Ardene Holdings Ltd | Financial services | 2026 |
| JLO Software Solutions Ltd | Information & communication | 2017 |
| Jlvet Ltd | Wholesale & retail | 2016 |
| JM Coring Limited | Construction | 2014 |
| JM Mcquillan Ltd | Construction | 2022 |
| Jmdawson Ltd | Health & social care | 2024 |
| JMF Services Limited | Professional & scientific | 2019 |
| JMH Holdings Direct Ltd | Real estate | 2024 |
| JMR Luxury Motors Ltd | Wholesale & retail | 2025 |
| JMT Plumbing Heating Ltd | Construction | 2023 |
| Jnat Ltd | Real estate | 2024 |
| Joanne E Carlin Ltd | Administrative & support | 2022 |
| JOB Done Right Limited | Information & communication | 2007 |
| John Campbell & Sons Limited | Construction | 2006 |
| John Hogg & Co, Limited | Professional & scientific | 1890 |
| John Hogg Pension Trustee Limited | Extraterritorial | 2000 |
| John Mcdowell (Lisburn) Limited | Health & social care | 2021 |
| John Mcquillan (Contracts) Limited | Construction | 1953 |
| John Preston & Co. (Belfast) Limited | Wholesale & retail | 1964 |
| John Preston & Co. (Holdings) | Financial services | 2016 |
| John Rainey & SON Limited | Manufacturing | 1949 |
| John Riddel and SON Limited | Transport & logistics | 1897 |
| Johnson Brothers (Belfast) Limited | Administrative & support | 1960 |
| Johnson Brothers (Distributing) Limited | Administrative & support | 1955 |
| Johnston 1969 Limited | Extraterritorial | 2013 |
| Johnston Contracts Ltd | Construction | 2011 |
| Johnston Pedlow Ltd | Construction | 2022 |
| Johnston Refrigeration Services Ltd | Manufacturing | 2017 |
| Joinery Estimating Ltd | Construction | 2019 |
| Joji's Ltd | Construction | 2023 |
| Jolly Rodgers Day Nursery Ltd | Other services | 2008 |
| Jomakat Ltd | Health & social care | 2018 |
| Jonami Limited | Wholesale & retail | 2026 |
| Joral Developments Ltd | Construction | 2007 |
| Jordan Concrete Ltd | Manufacturing | 1973 |
| Jordan's Gift | Administrative & support | 2016 |
| Joseph Magee & Co. Limited | Professional & scientific | 2019 |
| Joshua Harrison Limited | Wholesale & retail | 2025 |
| JPM Commercials Ltd | Construction | 2020 |
| JPN Logistics Holdings Limited | Professional & scientific | 2024 |
| JPN Logistics Ltd | Transport & logistics | 2010 |
| JPW Automotive Ltd | Wholesale & retail | 2026 |
| Jrts Developments Ltd | Construction | 2012 |