| Jp&Ctproperty Ltd | Real estate | 2025 |
| JP9 Limited | Real estate | 2024 |
| JPB Properties Limited | Real estate | 2019 |
| JPB Property Developments Ltd | Real estate | 2022 |
| JPB3 Limited | Real estate | 2021 |
| Jpbe Developments Limited | Real estate | 2017 |
| Jpbe Property Holdings Limited | Real estate | 2022 |
| JPD Design & Consultancy Services Limited | Professional & scientific | 2014 |
| Jphi Ltd | Construction | 2024 |
| JPM Plumbing and Heating Ltd | Construction | 2026 |
| Jpoh Trading (Neath) Ltd | Hospitality | 2021 |
| JPR Financial Limited | Financial services | 2008 |
| JPS Building Ltd | Construction | 2018 |
| JQ Estates Limited | Financial services | 2024 |
| JR & SL Estates Limited | Other services | 2009 |
| JR Property (Swansea) Limited | Real estate | 2019 |
| JRB Recovery Ltd | Transport & logistics | 2022 |
| Jrbd Property Ltd | Real estate | 2025 |
| JRD Fitness and Coaching Ltd | Education | 2025 |
| Jrees Properties Ltd | Real estate | 2026 |
| JRG Watts Limited | Real estate | 2022 |
| Jrhwelding Ltd | Professional & scientific | 2024 |
| Jritchie Trading Limited | Financial services | 2026 |
| Jrjelectrical Services Ltd | Construction | 2022 |
| JRO Services Limited | Health & social care | 2017 |
| Jrones Detect Ltd | Wholesale & retail | 2026 |
| Jrsmith Limited | Transport & logistics | 2024 |
| JRT Building & Landscaping Ltd | Construction | 2024 |
| JS & CS Consultancy Limited | Information & communication | 1997 |
| JS Ridley Limited | Construction | 2019 |
| JSB Property Developments Limited | Real estate | 2018 |
| JSE Swansea Holdings Limited | Financial services | 2024 |
| JSM Mechanicals Ltd | Construction | 2025 |
| JSM Security Ltd | Administrative & support | 2015 |
| JSS Traders Limited | Wholesale & retail | 2024 |
| JST Assets Limited | Households | 2026 |
| JSW - Serviced Apartments Ltd | Hospitality | 2017 |
| JT Care Solutions and Recruitment Ltd | Administrative & support | 2025 |
| JT Commercial and Domestic Cleaning Services Ltd | Administrative & support | 2022 |
| JT Elite Coaching Ltd | Education | 2024 |
| JT Independent EYE Limited | Wholesale & retail | 2023 |
| JT Lighting Limited | Information & communication | 2023 |
| JT Sound Limited | Information & communication | 2010 |
| Jt's Motorcycles Limited | Wholesale & retail | 2002 |
| Jt's Motoworx Ltd | Wholesale & retail | 2023 |
| JTC Carpentry Swansea Limited | Construction | 2025 |
| JTG Hospitality Ltd | Hospitality | 2016 |
| JTJ Enviroserve Ltd | Construction | 2026 |
| JTM Chiropractic Limited | Health & social care | 2013 |
| JTP Direct Ltd | Wholesale & retail | 2023 |
| JTR Plumbing Services Ltd | Construction | 2024 |
| JTV Hospitality Ltd | Hospitality | 2017 |
| Jubilee Dinner Limited | Hospitality | 2025 |
| Jubilee Garden (Wales) Limited | Hospitality | 2018 |
| Judah's Lion Ltd | Public administration | 2014 |
| Judicare Limited | Financial services | 2003 |
| Julescabs Ltd | Transport & logistics | 2003 |
| Julian James Cladding Limited | Administrative & support | 1993 |
| Julians Supermarkets Limited | Wholesale & retail | 1998 |
| Julie Llewellyn Limited | Education | 1994 |
| Jumiq Ltd | Administrative & support | 2025 |
| Juniper Tree Coffee Lounge Ltd | Hospitality | 2023 |
| Junrui International Trading Ltd | Wholesale & retail | 2021 |
| Jupiter Solutions Ltd | Wholesale & retail | 2023 |
| Jupiter Terra Ltd | Real estate | 2024 |
| Jurat Marketing Limited | Real estate | 1995 |
| Jusadeg Intl Ltd | Information & communication | 2023 |
| Jush Virtual Ltd | Information & communication | 2022 |
| Just Gents Hairdressers Limited | Other services | 2003 |
| Just Honey Wales Limited | Wholesale & retail | 2026 |
| Just in Time Plumbing, Heating & Building Services Limited | Construction | 2006 |
| Just LET ME NOW Ltd | Real estate | 2025 |
| Just One More Mushroom Ltd | Wholesale & retail | 2024 |
| JV Maranon Limited | Health & social care | 2016 |
| JV Soft Limited | Information & communication | 2014 |
| JVA Property Limited | Real estate | 2017 |
| JW Eynon Investments Ltd | Financial services | 2022 |
| JW Window Cleaning Services Limited | Administrative & support | 2025 |
| JWC Contractors Ltd | Construction | 2019 |
| JWM Electrical Services (Norfolk) Ltd | Energy | 2012 |
| Jwmd Holdings Limited | Real estate | 2023 |
| Jwmd Medical Limited | Health & social care | 2013 |
| JYA Properties (Wales) Limited | Real estate | 2025 |
| JYW Ysta Ltd | Hospitality | 2025 |
| J’Taime Ltd | Wholesale & retail | 2022 |
| K & J Contracting Ltd | Construction | 2024 |
| K & N Construction Limited | Construction | 2015 |
| K & N Contractors Ltd | Construction | 2023 |
| K & R Rentals Limited | Hospitality | 2026 |
| K and a Property Limited | Households | 2015 |
| K B Ferguson Limited | Professional & scientific | 2005 |
| K C Motors Limited | Wholesale & retail | 2003 |
| K D Crabb Limited | Construction | 2015 |
| K Hughes Homes Limited | Real estate | 2020 |
| K J Boxing Ltd | Arts & recreation | 2025 |
| K J Future Electrics Limited | Construction | 2023 |
| K J Hire and Sales Limited | Administrative & support | 2003 |
| K L & Partners Ltd | Real estate | 2016 |
| K L Management Services Limited | Real estate | 2024 |
| K M Carr Ltd | Professional & scientific | 2024 |