| High Voltage Construction and Management Ltd | Other services | 2024 |
| Hilltop Consulting Limited | Professional & scientific | 2018 |
| Hilltop Escapes Limited | Real estate | 2021 |
| Hilltop Property Ventures LLP | | 2021 |
| Hilltop PV Limited | Real estate | 2025 |
| Historicalwales Ltd | Wholesale & retail | 2022 |
| Hodge & Co Legal Limited | Professional & scientific | 2013 |
| Hogan Waste Limited | Water & waste | 2017 |
| Holmes and Murphy Limited | Professional & scientific | 2012 |
| Holocron Health Limited | Health & social care | 2026 |
| Homecare (Anglesey) Limited | Extraterritorial | 2012 |
| Hospitality Sols Ltd | Hospitality | 2024 |
| Hot Tech Limited | Extraterritorial | 2012 |
| House of Page Ltd | Information & communication | 2024 |
| House to Home Investments Ltd | Real estate | 2016 |
| Howell Energy Solutions Limited | Professional & scientific | 2018 |
| Howzat Catering Ltd | Hospitality | 2025 |
| HQA Consulting Ltd | Information & communication | 2022 |
| HTC Holdco Ltd | Real estate | 2025 |
| Hudson's Homes Limited | Real estate | 2020 |
| Hughes Heating & GAS Maintenance Ltd | Construction | 2021 |
| Hughes House and Hotel Painters Limited | Construction | 2025 |
| Humphreys Signs Limited | Manufacturing | 1989 |
| Hush Therapies Ltd | Health & social care | 2021 |
| HV Standby Solutions Ltd | Construction | 2019 |
| HVM Associates Limited | Administrative & support | 2011 |
| Hyfforddiant Enlli Training Ltd | Education | 2021 |
| IDB Engineering Services Limited | Professional & scientific | 2020 |
| IDB Systems Limited | Manufacturing | 2010 |
| Idolpopuk Limited | Wholesale & retail | 2023 |
| Iframe Online Ltd | Extraterritorial | 2016 |
| Ignite Engine Room Limited | Arts & recreation | 2025 |
| Ignite Gym NW Limited | Arts & recreation | 2022 |
| IKT International Association of Curators of Contemporary Art Ltd | Arts & recreation | 2022 |
| Impereo Ltd | Real estate | 2009 |
| Imperial Buildings 1894 Management Limited | Households | 2016 |
| IMPLEMENT4U Ltd | Professional & scientific | 2016 |
| Indian Kitchen Llandudno Ltd | Hospitality | 2024 |
| Indigo Taste Ltd | Hospitality | 2024 |
| Inklectic Tattoos Limited | Other services | 2014 |
| Innjoy Stay Ltd | Hospitality | 2022 |
| Innovation Hub Studio Ltd | Information & communication | 2026 |
| Insero Recruitment Limited | Administrative & support | 2017 |
| Integrate Therapy Ltd | Health & social care | 2011 |
| Intelenergy Ltd | Construction | 2025 |
| Interior Renovations Limited | Construction | 2003 |
| Interlink Taxis Limited | Transport & logistics | 2014 |
| Investors in Earth Ltd | Professional & scientific | 2021 |
| Irish Bar Ltd | Hospitality | 2014 |
| IT Business Networks Limited | Information & communication | 2025 |
| J & T Greaves Limited | Wholesale & retail | 2013 |
| J B-Monitor Limited | Professional & scientific | 2000 |
| J G & SON Limited | Construction | 2005 |
| J J Mobile Plant Repairs Ltd | Manufacturing | 2022 |
| J K Williams Limited | Transport & logistics | 2014 |
| J L Leisure Ltd | Wholesale & retail | 2002 |
| J P Mann Limited | Hospitality | 2012 |
| J Pratt & Co Ltd | Professional & scientific | 2015 |
| J R Lloyd Holdings CYF | Financial services | 2023 |
| J S J Marine CYF | Professional & scientific | 2020 |
| J&K High Voltage Maintenance Limited | Manufacturing | 2014 |
| J.Campbell Construction Limited | Construction | 2001 |
| JA Dwell Limited | Real estate | 2025 |
| Jackson Trade Services Ltd | Construction | 2026 |
| JAE Solutions Limited | Construction | 2016 |
| Jaher Miah Ltd | Professional & scientific | 2018 |
| Jamart Limited | Hospitality | 2018 |
| JAN Klin & Associates Ltd | Information & communication | 2007 |
| Jane EVA Homes Limited | Real estate | 2006 |
| JAR Architecture & Design Ltd | Professional & scientific | 2016 |
| JAS Training Solutions Ltd. | Education | 2024 |
| Jcblythin Ltd | Energy | 2023 |
| JD (Bangor) Ltd | Hospitality | 2023 |
| JEK Core Wind Ltd | Professional & scientific | 2026 |
| Jennings Renewable Solutions Ltd | Other services | 2017 |
| JGA Project Services Ltd | Professional & scientific | 2026 |
| JIM Emmerson Ltd | Administrative & support | 2016 |
| JJ Agricultural & Haulage Services Limited | Transport & logistics | 2026 |
| JJ Lettings Limited | Hospitality | 2014 |
| JL Smile 80 Ltd | Health & social care | 2023 |
| JM Distillations Limited | Wholesale & retail | 2018 |
| JMC Energy Ltd | Construction | 2017 |
| Jobscast Limited | Administrative & support | 2021 |
| Johnny Throws Ltd | Arts & recreation | 2023 |
| Joji Butt Ltd | Wholesale & retail | 2025 |
| Jona's Kitchen Ltd | Hospitality | 2021 |
| Jones Roofing North Wales and Cheshire Limited | Construction | 1999 |
| Jones Surgical Services Ltd | Health & social care | 2023 |
| Jonny Ross Music Ltd | Administrative & support | 2013 |
| Journolab Limited | Information & communication | 2008 |
| JP Developments NW Ltd | Construction | 2023 |
| JP Estates N.W Ltd | Construction | 2026 |
| JPL Heating Ltd | Construction | 2019 |
| JS Caravans Ltd | Wholesale & retail | 2018 |
| JSJ Property Limited | Hospitality | 2014 |
| Jsvk Limited | Real estate | 2023 |
| JT & RH Investments Limited | Hospitality | 2018 |
| JTC at Services Ltd | Manufacturing | 2023 |
| Jtsclient Ltd | Professional & scientific | 2026 |
| JVR Video Ltd | Information & communication | 2023 |