| Horizn Fitness Ltd | Arts & recreation | 2025 |
| Hotspot Outlet Ltd | Wholesale & retail | 2025 |
| House to Home Property Developments Ltd | Real estate | 2017 |
| Howfield Hotel Limited | Hospitality | 2024 |
| HSS Brickwork & Paving Limited | Construction | 2018 |
| Hughes Painting Contractors Limited | Construction | 2025 |
| Hughes Thomas Limited | Arts & recreation | 2022 |
| Hunter-Idzi Developments Ltd | Real estate | 2024 |
| Hydra Consultants Ltd | Professional & scientific | 2025 |
| Hydra Industries Limited | Financial services | 2026 |
| Hydra Scaffolding Ltd | Construction | 2025 |
| Hynes and SON Limited | Health & social care | 2020 |
| Hynes Felton Limited | Arts & recreation | 2017 |
| HZ Barbers Limited | Other services | 2024 |
| HZE Solutions Ltd | Construction | 2026 |
| I-Steel Limited | Manufacturing | 2011 |
| Ignition Publications Limited | Information & communication | 2003 |
| Ignition Sports Media Limited | Information & communication | 2013 |
| IJF Engineering Limited | Professional & scientific | 1997 |
| IMJ Holdings Limited | Financial services | 2025 |
| IMS Property Management Ltd | Real estate | 2021 |
| Indigo Safety Management Limited | Professional & scientific | 2020 |
| Industrial Door Components (Wales) Ltd | Manufacturing | 2017 |
| Inevus Advanced Analytics Ltd | Information & communication | 2023 |
| Infinity Resin Ltd | Construction | 2024 |
| Infinity Roofing & Building Ltd | Construction | 2017 |
| Inhome Design (Wales&West) Ltd | Wholesale & retail | 2015 |
| Insurance Services Wales Ltd. | Financial services | 1994 |
| Integral Fire Sprinklers Ltd | Public administration | 2017 |
| International Crown Events Ltd | Arts & recreation | 2021 |
| Internet Cars Wales Limited | Wholesale & retail | 2014 |
| INVEST2VALLEY Limited | Construction | 2017 |
| Invictus Health Limited | Administrative & support | 2019 |
| IPS ME Holdings Limited | Financial services | 2024 |
| IPS Mechanical Engineering Limited | Manufacturing | 2018 |
| Ipsme Group Ltd | Financial services | 2026 |
| IR Energy Holdings Limited | Construction | 2024 |
| IR Recruitment Ltd | Administrative & support | 2025 |
| Ironmaster CC Ltd | Hospitality | 2022 |
| ISA Bella Pizza Ltd | Hospitality | 2025 |
| Islwyn Pugh Construction Limited | Construction | 2005 |
| J & T Telecoms Ltd | Construction | 2024 |
| J and a World Class Properties Ltd | Real estate | 2021 |
| J and a World-Class Services Limited | Professional & scientific | 2011 |
| J and M Housing Limited | Real estate | 2024 |
| J B Properties Cardiff Ltd | Real estate | 2022 |
| J C Lynn Contracting Services Ltd | Administrative & support | 2017 |
| J C Thomas Welding Services Limited | Professional & scientific | 2025 |
| J E Management Ltd | Construction | 2016 |
| J Egan Haulage Limited | Transport & logistics | 2015 |
| J Hope Ltd | Construction | 2021 |
| J K S Auto Services Ltd | Wholesale & retail | 2022 |
| J R Properties Cardiff Limited | Real estate | 2026 |
| J Williams Heating and Plumbing Ltd | Construction | 2023 |
| J&J Garage Service's Ltd | Wholesale & retail | 2023 |
| J&L Refurb Limited | Construction | 2025 |
| J&L Utilities Ltd | Construction | 2024 |
| J&M Auto Locksmiths Ltd | Wholesale & retail | 2025 |
| J.D. Express Limited | Transport & logistics | 2002 |
| J.J.J. Properties Limited | Real estate | 2018 |
| J.K Firewood Ltd | Wholesale & retail | 2021 |
| Ja-Al Trade Ltd | Transport & logistics | 2018 |
| Jack Browne Coaching Limited | Arts & recreation | 2025 |
| Jack Browne Personal Training Ltd | Education | 2025 |
| JAD Property Investments Limited | Real estate | 2025 |
| Jade NEO Limited | Wholesale & retail | 2024 |
| JAE Carpentry Ltd | Manufacturing | 2022 |
| Jaffa Scenic Construction Ltd. | Construction | 2019 |
| Jall Contractors Ltd | Extraterritorial | 2012 |
| Jamar Building Ltd | Construction | 2025 |
| James Boulton Limited | Water & waste | 2004 |
| Jamie Charlton Ltd | Households | 2025 |
| Jamys Rooms Ltd | Hospitality | 2024 |
| Janway Construction Ltd | Construction | 2023 |
| JAS Freshfoods Ltd | Manufacturing | 2013 |
| Jassleen Limited | Wholesale & retail | 2026 |
| Jaxon Engineering Services Ltd | Professional & scientific | 2022 |
| Jay's Training & Consultancy Limited | Professional & scientific | 2009 |
| JB Footwear Ltd | Wholesale & retail | 2016 |
| JC & LC Holding Ltd | Financial services | 2023 |
| JC Davies Rail Ltd | Construction | 2015 |
| Jcdc Properties Ltd | Real estate | 2025 |
| Jdeprojects Limited | Construction | 2019 |
| Jenkins Heating Ltd | Construction | 2025 |
| Jentor Limited | Wholesale & retail | 2013 |
| JGF Properties Limited | Financial services | 2010 |
| JHB Associates Limited | Professional & scientific | 2008 |
| JHE System Services Ltd | Construction | 2022 |
| JIO Wales Properties Limited | Real estate | 2020 |
| JJ Coaching Consultancy Ltd | Education | 2025 |
| JJ NJC Ltd | Hospitality | 2024 |
| JJG Properties (Wales) Limited | Real estate | 2012 |
| Jjlc Cefn Cubs | Arts & recreation | 2025 |
| JK Fowler Financial Advice Ltd | Professional & scientific | 2020 |
| JK Same Day Delivery Ltd | Transport & logistics | 2022 |
| JKM Rail Services Ltd | Construction | 2022 |
| JLC Plant & Property Ltd | Real estate | 2024 |
| JLC Property Developer Limited | Real estate | 2022 |
| JLC Property Developments Ltd | Real estate | 2020 |
| JLD Media Limited | Manufacturing | 2008 |