| Jabbco Property Ltd | Construction | 2023 |
| JAC Accounting Solutions Ltd | Information & communication | 2008 |
| JAC Industries Limited | Financial services | 2018 |
| JAC Property & Investments Limited | Real estate | 2009 |
| Jaca Holdings Limited | Financial services | 2025 |
| Jaccad Ltd | Real estate | 2021 |
| Jack D Associates Ltd | Other services | 2024 |
| Jack D Holdings Limited | Financial services | 2023 |
| Jack Mcmillan Swim Ltd | Education | 2025 |
| Jack Morrison Ltd | Wholesale & retail | 2023 |
| Jack Murphy Consulting Ltd | Information & communication | 2021 |
| Jackey Holdings Ltd | Real estate | 2018 |
| Jackie Mcmahon Limited | Administrative & support | 2017 |
| Jacks Retailing Ltd | Wholesale & retail | 2019 |
| Jackson Dental Limited | Health & social care | 2023 |
| Jackson Oliver James Ltd | Wholesale & retail | 2025 |
| Jackson South Limited | Financial services | 2014 |
| Jackson Sports Limited | Wholesale & retail | 2003 |
| Jackson Ventures Limited | Arts & recreation | 2012 |
| Jacobs Health Ltd | Health & social care | 2023 |
| Jacobsen Investments Limited | Real estate | 2000 |
| Jacque Healthcare Limited | Health & social care | 2024 |
| Jacqueline Rooney Art Ltd | Arts & recreation | 2022 |
| Jade Belfast Ltd | Hospitality | 2025 |
| Jade Orla Agencies Ltd | Professional & scientific | 2022 |
| JADE3 382 Ltd | Hospitality | 2018 |
| Jadepeakq Limited | Wholesale & retail | 2025 |
| Jaevzgi Limited | Wholesale & retail | 2025 |
| JAF Developments Limited | Real estate | 1995 |
| JAF H Construction Ltd | Construction | 2025 |
| JAG Aviation Logistics Limited | Professional & scientific | 2018 |
| Jago Communications Ltd | Professional & scientific | 2012 |
| Jago Technology Ltd | Information & communication | 2022 |
| Jahid Hasan Ltd | Wholesale & retail | 2024 |
| Jaja Electrical Ltd | Manufacturing | 2019 |
| JAK Square Events LLP | | 2024 |
| Jaks Belfast - Joinery and Kitchen Services Ltd | Construction | 2022 |
| Jalla Metal Repairs Ltd | Wholesale & retail | 2026 |
| JAM Lettings Limited | Hospitality | 2025 |
| JAM Media (Northern Ireland) Limited | Information & communication | 2013 |
| JAM Toys Limited | Wholesale & retail | 2023 |
| Jamb Group Ltd | Professional & scientific | 2024 |
| James & Co Stocktakers Limited | Administrative & support | 2022 |
| James Alexander Automotive Ltd | Wholesale & retail | 2021 |
| James Allen and Company (Belfast) Limited | Extraterritorial | 1937 |
| James Arthur Ross Limited | Manufacturing | 2022 |
| James Cable Ltd | Wholesale & retail | 2024 |
| James Clow & Co Limited | Wholesale & retail | 1919 |
| James Clow Apartments Management Company Limited | Households | 2007 |
| James Connor Ltd | Wholesale & retail | 2025 |
| James Donnelly & Sons Ltd | Wholesale & retail | 2002 |
| James Donnelly Ltd | Transport & logistics | 2014 |
| James E Donnelly Ltd | Wholesale & retail | 2025 |
| James Gary Limited | Manufacturing | 2024 |
| James Glennon Packaging Limited | Manufacturing | 1993 |
| James Grieve Architects Ltd | Professional & scientific | 2024 |
| James Gumble Ltd. | Information & communication | 2015 |
| James H. Givan Limited | Wholesale & retail | 1979 |
| James Logan Cars Limited | Wholesale & retail | 1999 |
| James MP Campbell Ltd | Wholesale & retail | 2022 |
| James P. Gardner & SON Limited | Real estate | 1946 |
| James Reid Construction Limited | Construction | 2005 |
| James Rolston & Co. Limited | Wholesale & retail | 1984 |
| James Sasan Ltd | Wholesale & retail | 2024 |
| James Scott Asset Management LLP | | 2013 |
| James Street Developments Limited | Real estate | 2024 |
| James Street Films Limited | Information & communication | 2014 |
| James Tolland Group Limited | Wholesale & retail | 2018 |
| James Warsop Trading Ltd | Wholesale & retail | 2024 |
| James Wright- Building Surveyors Ltd | Professional & scientific | 2025 |
| James Xavier Limited | Wholesale & retail | 2024 |
| Jameson Creative Digital Marketing Limited | Professional & scientific | 2021 |
| Jamie Care Services Ltd | Health & social care | 2026 |
| Jamie Sinclair Hair Ltd | Other services | 2022 |
| Jamieson Electrical Technologies (J.E.T.) Limited | Manufacturing | 2015 |
| Jamil Tiantian Ltd | Wholesale & retail | 2024 |
| Jamilleri Limited | Extraterritorial | 2014 |
| Jamjum Limited | Wholesale & retail | 2024 |
| Jammark Limited | Hospitality | 2024 |
| Jan's Mart Ltd | Hospitality | 2025 |
| Janeke Marte Ltd | Wholesale & retail | 2024 |
| Jangmi Holdings Ltd | Health & social care | 2024 |
| Janiveer Investments Limited | Professional & scientific | 2015 |
| Jannat Belfast Limited | Hospitality | 2020 |
| Jans Composites Ltd | Manufacturing | 2019 |
| Jans Finance Limited | Financial services | 2021 |
| Jans Offsite Solutions Limited | Construction | 2021 |
| Jantech Ltd | Information & communication | 2021 |
| Japp Holdings Ltd | Professional & scientific | 2024 |
| Japsd Ltd | Financial services | 2025 |
| Japuro Ltd | Wholesale & retail | 2024 |
| Jaq-In-The-Box Ltd | Arts & recreation | 2025 |
| JAR (IRE) Ltd | Administrative & support | 2012 |
| JAR Supplies Ltd | Manufacturing | 2010 |
| Jaras Property Developments Limited | Professional & scientific | 2001 |
| Jardin STT Limited | Financial services | 2021 |
| JAT (NO.1) Limited | Financial services | 2013 |
| JAT (NO.3) Limited | Financial services | 2013 |
| Javed Kingsway Ltd | Hospitality | 2025 |
| Javian Ltd | Construction | 2022 |