| H Retail Express Ltd | Wholesale & retail | 2018 |
| Haddon Training Limited | Education | 2003 |
| Hair Lair Extensions Limited | Other services | 2024 |
| Hair.Com (Wales) Limited | Information & communication | 2004 |
| Haji Mini Market Ltd | Wholesale & retail | 2024 |
| Haley's Bakes and Cakes Limited | Manufacturing | 2022 |
| Halzac Properties Ltd | Real estate | 2026 |
| Hangry Animals Ltd | Information & communication | 2022 |
| Harrent Properties Ltd | Real estate | 2016 |
| Hedlunds Property and Energy Ltd | Construction | 2008 |
| Hengoed 100 Limited | Hospitality | 2025 |
| Hengoed Kebab Ltd | Hospitality | 2024 |
| Hengoed Spice Ltd | Hospitality | 2022 |
| Hens Step Ventures Ltd | Wholesale & retail | 2026 |
| HMR Metals Limited | Wholesale & retail | 2021 |
| Holiday With Emma Limited | Administrative & support | 2022 |
| Holness Connect Ltd | Information & communication | 2011 |
| Horlicks Installations Ltd | Manufacturing | 2026 |
| Horsman Design Ltd | Construction | 2002 |
| Hotset UK Limited | Manufacturing | 1993 |
| House Clearance Caerphilly Limited | Administrative & support | 2019 |
| Howells Training Ltd | Education | 2018 |
| Hudson & HAY Ltd | Wholesale & retail | 2025 |
| Hudson Alykes Ltd | Real estate | 2025 |
| IAN D Richards Consulting Ltd | Professional & scientific | 2024 |
| Ieuan Murrell Ltd | Transport & logistics | 2026 |
| Ihselectrical Limited | Construction | 2025 |
| IKA Properties Limited | Real estate | 2022 |
| Independent Housing and Care Consultancy Services Ltd | Real estate | 2018 |
| Industrial Construction Products Ltd | Manufacturing | 2017 |
| IP Mortgages Ltd | Financial services | 2018 |
| ISA Training Limited | Education | 1998 |
| J C Booth Limited | Real estate | 1998 |
| J G Design Limited | Professional & scientific | 2014 |
| J N Stores Ltd | Wholesale & retail | 2020 |
| J5 Capital Properties Ltd | Real estate | 2025 |
| Jaybee Housing Ltd | Real estate | 2024 |
| Jayne Private Limited | Health & social care | 2024 |
| JD Rentals Limited | Hospitality | 2020 |
| Jelly Bean Ltd | Administrative & support | 2014 |
| Jenks Autocare Limited | Manufacturing | 2020 |
| JGG Carpentry Services Limited | Construction | 2014 |
| JJE Floors Limited | Construction | 2015 |
| JM Pest Solutions Ltd | Administrative & support | 2024 |
| Jones & Sons Property Reporting Ltd | Construction | 2023 |
| JPR Phoenix Ltd | Administrative & support | 2007 |
| Jual Furnishings Limited | Manufacturing | 2006 |
| Jual Limited | Extraterritorial | 2008 |
| Jwills Property Ltd | Real estate | 2026 |
| K T Fencing Limited | Construction | 2001 |
| K&B Holding Ltd | Financial services | 2023 |
| Kaibren Pipe Ltd | Professional & scientific | 2025 |
| Kane Business Systems Limited | Transport & logistics | 1991 |
| Kane Cloud Comms Limited | Information & communication | 2023 |
| Kane Group Holdings Limited | Financial services | 2021 |
| Kane Mailing Systems Ltd | Administrative & support | 1994 |
| Karina Krafts Limited | Wholesale & retail | 2001 |
| Kendon Automotive Limited | Professional & scientific | 1999 |
| Key Logistics Ltd | Transport & logistics | 2025 |
| KR Home Improvements Ltd | Construction | 2025 |
| Kripasanam Services Ltd | Transport & logistics | 2026 |
| KTS Tyres Limited | Wholesale & retail | 2004 |
| Kyniog Ltd | Wholesale & retail | 2021 |
| L & G Brewer Property Limited | Real estate | 2024 |
| L E Starsignings Ltd | Wholesale & retail | 2025 |
| L J D Williams Ltd | Financial services | 2024 |
| L.T.J Group Limited | Financial services | 2020 |
| Legends of Sport Ltd | Arts & recreation | 2015 |
| LEL Delivers Ltd | Other services | 2019 |
| Lewis Drainage Limited | Construction | 2007 |
| Linked Media Ltd | Professional & scientific | 2020 |
| Lisa Davies Legal Services for Children | Professional & scientific | 2014 |
| Little Acorns Preschool (Caerphilly) Ltd | Education | 2017 |
| Lloyd Perry Investments Limited | Real estate | 2021 |
| Lola's Lunchbox Ltd | Hospitality | 2025 |
| Longlife Cardiff Exhausts Ltd | Wholesale & retail | 2010 |
| Lordan (UK) Ltd. | Manufacturing | 2003 |
| LPS Services Limited | Manufacturing | 2000 |
| LSD Motorsport Ltd | Wholesale & retail | 2024 |
| Ltd Fitness Limited | Arts & recreation | 2024 |
| Lucas & Clash Mortgages Ltd | Professional & scientific | 2021 |
| Lucas Estates Ltd | Real estate | 2008 |
| Lucky Valley Limited | Hospitality | 2012 |
| Lunar Computers Limited | Wholesale & retail | 2022 |
| Luxurious LOX Ltd | Other services | 2026 |
| Lynton Community Care Limited | Health & social care | 2001 |
| Lyra Industrial Refrigeration Ltd | Construction | 2025 |
| M G Rigging Limited | Construction | 2019 |
| M.V. Plastering Limited | Construction | 2015 |
| Maesy Spice Ltd | Hospitality | 2026 |
| Malpaspantry Limited | Hospitality | 2025 |
| Manorcraft Interior Systems Limited | Construction | 2007 |
| Manorcraft Limited | Construction | 2007 |
| Marigold Coaching Limited | Administrative & support | 2016 |
| Marmaris Barber Shop #2 Ltd | Other services | 2017 |
| Martin J Anderson Limited | Financial services | 2014 |
| Mastercontrol Systems Ltd | Manufacturing | 2018 |
| Masterdesign Solutions Ltd | Professional & scientific | 2020 |
| Matel Communications Limited | Information & communication | 2019 |
| Mayo Property Development Limited | Administrative & support | 2007 |