| IT Takeaway Ltd | Hospitality | 2024 |
| Italia Food Limited | Wholesale & retail | 2023 |
| Ithink Welfare CIC | Health & social care | 2021 |
| Itsy Bitsy Ltd | Professional & scientific | 2025 |
| Ittehad Ltd | Wholesale & retail | 2020 |
| IV Invest Ltd | Wholesale & retail | 2025 |
| Ivan & Co Ltd | Hospitality | 2014 |
| IVD Heating Ltd | Construction | 2022 |
| Ivolve CC Ltd | Health & social care | 2005 |
| Ivolve CMC Ltd | Health & social care | 2004 |
| Ivolve DC Ltd | Health & social care | 2014 |
| Ivolve TY Newydd Ltd | Health & social care | 2019 |
| Ivolve Wales Head Office Ltd | Professional & scientific | 2019 |
| IVY & FOX Ltd | Extraterritorial | 2012 |
| IVY League Homes Ltd | Administrative & support | 2016 |
| Iweigh Limited | Professional & scientific | 2011 |
| Izone Software Limited | Information & communication | 2016 |
| I’M a Digital Nomad Ltd | Professional & scientific | 2024 |
| J & S Builders (Swansea) Limited | Construction | 2021 |
| J & a Electrical Services Ltd | Construction | 2013 |
| J & I Property Ltd | Real estate | 2019 |
| J & J Air Conditioning Refrigeration Ltd | Construction | 2025 |
| J & J Phillips Financial Planning Ltd | Financial services | 2020 |
| J & J Services Swansea Limited | Professional & scientific | 2014 |
| J & L Scaffolding (Wales) Limited | Construction | 2006 |
| J & M Sullivan Limited | Construction | 2019 |
| J & R (Mumbles) Limited | Hospitality | 2012 |
| J & T Homes Ltd | Real estate | 2026 |
| J a Locke Ltd | Manufacturing | 2025 |
| J and H Traders Limited | Hospitality | 2025 |
| J and J Motor Sales Ltd | Wholesale & retail | 2015 |
| J and J Property Development Ltd | Real estate | 2025 |
| J Andrews Properties Limited | Real estate | 2022 |
| J B & Family Properties Limited | Real estate | 2023 |
| J B Business Services (Swansea) Limited | Administrative & support | 2012 |
| J C Davies Limited | Construction | 2015 |
| J C Morgan Services Ltd | Other services | 2016 |
| J C Williams Developments Wales Limited | Construction | 2018 |
| J Carpentry Ltd | Construction | 2023 |
| J Cubitt Limited | Health & social care | 2023 |
| J Cursio Property Ltd | Real estate | 2015 |
| J D Baylis Limited | Wholesale & retail | 2007 |
| J D Electrical (Swansea) Ltd | Construction | 2024 |
| J D Hughes Holdings Limited | Financial services | 2019 |
| J D Jones Metals Ltd | Wholesale & retail | 2019 |
| J D Squared Properties Limited | Real estate | 2025 |
| J Evans Services Limited | Construction | 2018 |
| J Gomes & Co Ltd | Real estate | 2025 |
| J Gwynn Limited | Professional & scientific | 2008 |
| J Hall Plumbing and Heating Ltd | Construction | 2007 |
| J Hill Hair Limited | Other services | 2021 |
| J Howells Property Ltd | Real estate | 2021 |
| J Hughes Group Limited | Financial services | 1935 |
| J Hunt Fine Foods Limited | Manufacturing | 2014 |
| J J Baileys Ltd | Wholesale & retail | 2025 |
| J J Care Consultants Ltd | Administrative & support | 2022 |
| J L J J Limited | Professional & scientific | 2014 |
| J L Jones Holdings Limited | Financial services | 2024 |
| J L Prestige Plumb Limited | Construction | 2020 |
| J L Taxation Services Ltd | Professional & scientific | 2002 |
| J Lynch Building Limited | Construction | 2020 |
| J Lynch Property Ltd | Real estate | 2019 |
| J M Properties Holdings Ltd | Real estate | 2025 |
| J Mark Evans Limited | Professional & scientific | 2010 |
| J P Davies Management Limited | Manufacturing | 2015 |
| J P Residences Ltd | Real estate | 2025 |
| J P Velardo Limited | Construction | 2004 |
| J Parkhouse Property Ltd | Real estate | 2022 |
| J S Gower Group Limited | Wholesale & retail | 2024 |
| J S Pubs Ltd | Hospitality | 2019 |
| J T Performance Ltd | Manufacturing | 2015 |
| J T Potter Properties Limited | Real estate | 2024 |
| J Trew Consulting Ltd | Professional & scientific | 2023 |
| J W & R Commercial Laundry Limited | Other services | 2023 |
| J W Eynon Ltd | Financial services | 2013 |
| J Webb Practice Ltd | Health & social care | 2015 |
| J&A Property Holdings and Management Ltd | Construction | 2026 |
| J&C Ventures Ltd | Real estate | 2024 |
| J&E Lewis Properties Limited | Hospitality | 2026 |
| J&F Elements Ltd. | Construction | 2017 |
| J&H Living Solutions Ltd | Real estate | 2025 |
| J&K Properties Ltd | Real estate | 2020 |
| J&K Weighing Systems Limited | Manufacturing | 2007 |
| J&L Listings Ltd | Real estate | 2024 |
| J&L Tidal Developments Ltd | Construction | 2023 |
| J&L Tidal Properties Ltd | Real estate | 2025 |
| J&M Construction (SW) Limited | Construction | 2022 |
| J&P Building Contractors Ltd | Construction | 2023 |
| J&R Carpentry & Building Ltd | Construction | 2020 |
| J&R Electrical Services Ltd | Construction | 2016 |
| J&S Apparel Limited | Manufacturing | 2016 |
| J&S Havenstone Investments Ltd | Real estate | 2025 |
| J&S Properties (Midlands) Ltd | Real estate | 2022 |
| J&S Rees Property Limited | Real estate | 2026 |
| J&V Handyman Service Ltd | Construction | 2022 |
| J&W Perfectclean Limited | Administrative & support | 2022 |
| J'S Foodstores Limited | Wholesale & retail | 2004 |
| J-B-W Technician Ltd | Manufacturing | 2025 |
| J. Collins Construction Limited | Construction | 2016 |
| J. Collins Homes Limited | Real estate | 2021 |