| Hoardings Limited | Manufacturing | 2020 |
| Hoardings.Wales Limited | Manufacturing | 2020 |
| Hobdv Limited | Health & social care | 2025 |
| Holdshare Limited | Financial services | 2026 |
| Hollis Plumbing and GAS Limited | Construction | 2015 |
| Hollis Property and Developments Ltd | Real estate | 2022 |
| Hopyard Meadow Cowbridge Management Limited | Households | 1984 |
| Horse and Groom 18 Limited | Hospitality | 2018 |
| Horton Motorsport Ltd | Wholesale & retail | 2020 |
| Hospitality Playbook Ltd | Professional & scientific | 2025 |
| Housley Williams Limited | Professional & scientific | 2025 |
| Howsarlock Limited | Other services | 2006 |
| Hugh Price Consulting Limited | Professional & scientific | 2010 |
| Hurryflow Limited | Hospitality | 1991 |
| I-Commercial Finance Limited | Professional & scientific | 2017 |
| I-Property Finance Limited | Professional & scientific | 2010 |
| Iains Kitchen Ltd | Hospitality | 2014 |
| IBO Promotions Limited | Manufacturing | 2014 |
| IBO Sound & Communications Ltd | Wholesale & retail | 2023 |
| ID Energy Services Wales Ltd | Construction | 2018 |
| Ieuan R Jones Ltd | Information & communication | 2019 |
| Iguana Property Limited | Real estate | 2022 |
| IN Time Electrical Limited | Construction | 2016 |
| IN Time Holdings Ltd | Real estate | 2021 |
| Infographics Limited | Manufacturing | 1973 |
| Inform Architecture Ltd | Professional & scientific | 2014 |
| Information Security Expert Group Limited | Professional & scientific | 2019 |
| Insideout Trading Ltd | Construction | 2021 |
| Integrity Mobility Solutions Ltd | Wholesale & retail | 2022 |
| Introsport Trust | Education | 2010 |
| Ipswich 102 Ltd | Information & communication | 2018 |
| Iron Anchor Holdings Ltd | Financial services | 2024 |
| Iron Anchor Marine Services Ltd | Other services | 2023 |
| Ironwood Stoves Limited | Extraterritorial | 2020 |
| Irving Engineering Enterprises Limited | Professional & scientific | 2005 |
| Ispec Engineering Limited | Professional & scientific | 2023 |
| J C Rolling Limited | Professional & scientific | 2022 |
| J M Rolling Limited | Other services | 2012 |
| J R Rolling Limited | Transport & logistics | 2022 |
| J T Paint and Bodyworks Ltd | Wholesale & retail | 2023 |
| J. Tech (Cardiff) Limited | Information & communication | 2007 |
| Jack Chandrinos Music Ltd | Arts & recreation | 2024 |
| Jack Rail Limited | Construction | 2017 |
| JAM Creative Studios Ltd. | Information & communication | 2010 |
| James Jenkins Limited | Construction | 2009 |
| James Matthews Graphic Design Ltd | Professional & scientific | 2023 |
| Jamjar Holdings Limited | Real estate | 2025 |
| Jamjar PR Limited | Professional & scientific | 2012 |
| JB Perry Ltd | Manufacturing | 2026 |
| JCB Animal Physio Ltd | Professional & scientific | 2023 |
| JEG Management Consulting Ltd | Professional & scientific | 2012 |
| Jenna Fulford Copywriter Ltd | Professional & scientific | 2026 |
| Jenson Developments (South Wales) Limited | Real estate | 2011 |
| Jewell & Petersen Limited | Financial services | 2004 |
| JJS Consultancy Ltd | Professional & scientific | 2018 |
| JM Countryside and Gardening Services Ltd | Administrative & support | 2021 |
| JMT (Cowbridge) Ltd | Professional & scientific | 2023 |
| JO Sullivan Research Services Ltd | Professional & scientific | 2012 |
| Joanna Alice Wilkins Property Limited | Real estate | 2022 |
| Joanne Fisher Law Limited | Administrative & support | 2015 |
| John Mahoney Limited | Administrative & support | 2009 |
| JON IAN Limited | Wholesale & retail | 1971 |
| JON James Studio Architecture Limited | Professional & scientific | 2020 |
| JON Williams Film Limited | Arts & recreation | 2010 |
| Jorda Limited | Wholesale & retail | 2011 |
| Jorge Powell Ltd | Information & communication | 2019 |
| Joyce and James Limited | Professional & scientific | 2024 |
| JPJ Dance Ltd | Education | 2021 |
| JRT Holdings Limited | Professional & scientific | 2007 |
| Juuv Limited | Hospitality | 2023 |
| K.J.A.Dark and SON Stone Masonry T/A Kinsale Stone Co Ltd | Manufacturing | 2025 |
| K.L.S. Golf Limited | Wholesale & retail | 2006 |
| Kaembeth Ltd | Hospitality | 2024 |
| Kamed Limited | Professional & scientific | 2014 |
| Karen Ashley Limited | Arts & recreation | 2002 |
| Kart Kingdom Limited | Arts & recreation | 2024 |
| Kassoe Housing UK Ltd | Administrative & support | 2016 |
| Kavanagh Hicks Ltd | Professional & scientific | 2018 |
| Kees Capital Ltd | Real estate | 2024 |
| Keith Bellamy Associates Limited | Information & communication | 2013 |
| Keystone Consulting Engineers Limited | Construction | 2012 |
| KH Roofing Services Limited | Construction | 2005 |
| Kingshill (Bristol) Residential Developments Limited | Real estate | 2020 |
| Kingshill Property Group Limited | Real estate | 2020 |
| Kingshill Residential Property Investment Limited | Real estate | 2020 |
| Kiwi Kitchen Design Limited | Manufacturing | 2019 |
| KP Agri Ltd | Manufacturing | 2017 |
| Kubutana Safari Ltd | Administrative & support | 2026 |
| Kurd Barbers Cowbridge Ltd | Other services | 2026 |
| L.W. Kitchens & Bathrooms Ltd | Other services | 2019 |
| Laceify Ltd | Extraterritorial | 2023 |
| LCE Enterprises Ltd | Other services | 2024 |
| Leabold Investments Limited | Professional & scientific | 2004 |
| Leanne Sokolski Consultancy Limited | Administrative & support | 2014 |
| LET by Frank Limited | Real estate | 2021 |
| LEV Group Holdings Limited | Professional & scientific | 2009 |
| Levco 2 Limited | Financial services | 2021 |
| Lewis Homes ( Meadow View) Limited | Construction | 2022 |
| Lewis Homes (South Wales) Limited | Construction | 2005 |
| Lewis Homes (Woodlands Green) Limited | Construction | 2019 |