| J & J Leisure Ltd | Arts & recreation | 2007 |
| J & SR Developments Ltd | Construction | 2016 |
| J & SR Properties Ltd | Real estate | 2025 |
| J Lewis Electrical Limited | Construction | 2016 |
| J2 Health & Nutrition Ltd | Professional & scientific | 2015 |
| Jala Taish Enterprize Ltd | Hospitality | 2019 |
| James Field Service Solutions Limited | Professional & scientific | 2015 |
| Jarman Constuction Maintenance Group Ltd | Construction | 2025 |
| Jashvi Ltd | Wholesale & retail | 2021 |
| JB Shield Security Ltd | Administrative & support | 2024 |
| Jeff Davies Carpets Limited | Wholesale & retail | 2003 |
| JHS Timber Frames Limited | Manufacturing | 2021 |
| JJF Property Ltd | Real estate | 2025 |
| Jmb's Kitchen Ltd | Hospitality | 2025 |
| Jmprimeestates Ltd | Real estate | 2024 |
| Joscal Ltd | Wholesale & retail | 2022 |
| Joy Creative Limited | Information & communication | 2014 |
| JSP Training & Coaching Ltd | Professional & scientific | 2022 |
| JT Safety Critical Ltd | Construction | 2016 |
| Kakf Barbers Ltd | Other services | 2026 |
| Kannatonia Ltd | Other services | 2023 |
| KAT Group Ltd | Health & social care | 2026 |
| Kate’S K9 Crew Ltd | Agriculture & fishing | 2025 |
| KD Cleaning Services Ltd | Administrative & support | 2024 |
| Keywork Recruitment Ltd | Administrative & support | 2021 |
| KJ Aesthetician Ltd | Other services | 2022 |
| KJT Catering Limited | Hospitality | 2014 |
| KKJ Rail Limited | Construction | 2018 |
| KM and EL Jenkins Limited | Financial services | 2026 |
| KMC Autoworks Ltd | Wholesale & retail | 2025 |
| KNN Barbers Ltd | Other services | 2026 |
| KSL Scaffolding Limited | Construction | 2015 |
| KT Surfacing Ltd | Construction | 2021 |
| L & L Courier and Removal Services Ltd | Transport & logistics | 2023 |
| L a Plant Sales Ltd | Wholesale & retail | 2025 |
| L J Civils Limited | Construction | 2026 |
| L.Aspray Ltd | Extraterritorial | 2022 |
| LA Style Windows and Doors Ltd | Construction | 2024 |
| Laser Minicoach & Minitravel Ltd | Transport & logistics | 2006 |
| Lateish Drinks Ltd | Wholesale & retail | 2023 |
| Launchpad Advisory Limited | Professional & scientific | 2026 |
| LBB Pathways C.I.C. | Education | 2025 |
| Lear & Sons Contracting Ltd | Construction | 2017 |
| Lewis Motorsport Ltd | Information & communication | 2024 |
| LI Hang Limited | Hospitality | 2024 |
| Lightfall Expeditions Ltd | Education | 2026 |
| Lilel Rail Planning Services Ltd | Construction | 2016 |
| Lisnagarvey Court Limited | Real estate | 2010 |
| Llwynypia Office Hub Limited | Administrative & support | 2019 |
| LN Carpentry and Building Ltd | Construction | 2025 |
| Lonic Electrical Ltd | Construction | 2023 |
| Luxe Cleaning Services Ltd | Administrative & support | 2025 |
| M & L Prime Estates Ltd | Real estate | 2025 |
| M & P Contractors Wales Limited | Construction | 1999 |
| M J R Drylining Ltd | Construction | 2022 |
| M&B Property Developments Ltd | Real estate | 2024 |
| M&K Pressure Washing Services Ltd | Administrative & support | 2025 |
| M&L Group Holdings Ltd | Financial services | 2020 |
| M&L Mechanical & Electrical Services Ltd | Construction | 2025 |
| MA & O Limited | Construction | 2022 |
| MAC Home Improvements Limited | Construction | 1998 |
| Maintain & Clean Ltd | Households | 2023 |
| Mar-Ray Estates Limited | Real estate | 1991 |
| Mario Car Body Shop Limited | Wholesale & retail | 2025 |
| Mcculloch Pitts Limited | Wholesale & retail | 2020 |
| Md's Procurement Co Ltd | Wholesale & retail | 2025 |
| Merriott`S Food Store Limited | Wholesale & retail | 2008 |
| Mid-Glam Decorators Limited | Construction | 1979 |
| Mitch Davies Aviation Ltd | Manufacturing | 2026 |
| MLB Transport Ltd | Transport & logistics | 2025 |
| MO Auto Body Shop Ltd | Wholesale & retail | 2024 |
| Moonbeam Penygraig Limited | Other services | 2025 |
| Mora Chauffeurs Prestige Limited | Transport & logistics | 2023 |
| MP Elegant Beauty Ltd | Other services | 2025 |
| MR Creemy Limited | Wholesale & retail | 2012 |
| MR. Skin Aesthetics Ltd | Other services | 2024 |
| Myramsapp Ltd | Information & communication | 2024 |
| N&K Kitchens Limited | Construction | 2018 |
| Napier Training Associates Limited | Professional & scientific | 2014 |
| Natural & Healthy UK Ltd | Wholesale & retail | 2018 |
| NC Spirits Limited | Wholesale & retail | 2025 |
| ND Electrical Solutions Ltd | Extraterritorial | 2024 |
| New Garden Meals Limited | Hospitality | 2015 |
| New Generation Electrical Ltd | Professional & scientific | 2021 |
| Newcore Healthcare Limited | Health & social care | 2014 |
| Newcore Limited | Health & social care | 2014 |
| Nisa Barber Ltd | Other services | 2023 |
| NOM NOM Express Ltd | Hospitality | 2024 |
| Norr Soder Developments Ltd | Construction | 2026 |
| NSK Stores Ltd | Wholesale & retail | 2019 |
| Old Central Stores Ltd | Wholesale & retail | 2025 |
| Open Realm Books Ltd | Information & communication | 2024 |
| Optimum Admin Services Limited | Administrative & support | 2015 |
| Osborne Estate Agents Limited | Real estate | 2011 |
| Oxford House Veterinary Clinic Ltd | Professional & scientific | 2022 |
| Oyes Tonypandy Ltd | Hospitality | 2025 |
| P H Chavda Ltd | Hospitality | 2026 |
| P.B.M. Services Limited | Construction | 2019 |
| Pandy Car Wash Ltd | Administrative & support | 2025 |
| Pandy Hand Car Wash Ltd | Administrative & support | 2026 |