| 360 Camera Limited | Information & communication | 2007 |
| 360 Degrees Management Limited | Professional & scientific | 2020 |
| 360 Electrical Contracting Ltd | Information & communication | 2016 |
| 360 Firm Ltd | Wholesale & retail | 2019 |
| 360 Models Limited | Wholesale & retail | 2017 |
| 360 Recruit Agency Limited | Administrative & support | 2019 |
| 360 Vehicle Solutions Ltd | Wholesale & retail | 2025 |
| 360CA Ltd | Information & communication | 2023 |
| 360FIZZ Ltd | Arts & recreation | 2018 |
| 360TRADEHUB Limited | Information & communication | 2021 |
| 365 ADS Ltd | Information & communication | 2025 |
| 365 Days of Limited | Health & social care | 2019 |
| 365 Electrical Installations Ltd | Construction | 2011 |
| 365 Energy Group Limited | Construction | 2025 |
| 365 Foods Limited | Administrative & support | 2018 |
| 365 Gainz Limited | Arts & recreation | 2015 |
| 365 Ground Utilities Ltd | Construction | 2019 |
| 365 Motor Finance Limited | Financial services | 2019 |
| 365 Publications Limited | Information & communication | 2019 |
| 365 Valet Ltd | Transport & logistics | 2022 |
| 369 Trading Group Ltd | Professional & scientific | 2020 |
| 37 Heol Llanishen Fach (Management) Limited | Households | 2020 |
| 37 Hornsey Park Road Residents Limited | Households | 2008 |
| 37/39A Cathedral Road Holdings Ltd | Financial services | 2018 |
| 38 Lower Cathedral Road Limited | Professional & scientific | 2008 |
| 39 MDB Ltd | Hospitality | 2024 |
| 39SMC Ltd | Real estate | 2023 |
| 3A Consult UK Ltd | Administrative & support | 2016 |
| 3A Property Investments Limited | Real estate | 2023 |
| 3CG Scaffolding Limited | Professional & scientific | 2019 |
| 3CORE Services Ltd | Construction | 2017 |
| 3CUBED Search Ltd | Administrative & support | 2016 |
| 3D Care (Cardiff) Limited | Health & social care | 2005 |
| 3D Community Care Limited | Education | 1997 |
| 3D Housing Ltd | Real estate | 2024 |
| 3D Pharma Consulting Ltd | Professional & scientific | 2019 |
| 3D Print Land Ltd | Manufacturing | 2023 |
| 3D Special SVS Limited | Health & social care | 2017 |
| 3D Synergy Ltd | Professional & scientific | 2022 |
| 3DDENTISTRY Limited | Health & social care | 2017 |
| 3DEVELOPERS Ltd | Real estate | 2015 |
| 3E Energy Project 3 Ltd | Construction | 2025 |
| 3E Global Trade Ltd | Wholesale & retail | 2023 |
| 3FOX International Limited | Information & communication | 2004 |
| 3HD Engineering Limited | Manufacturing | 2021 |
| 3JC Enterprise Ltd | Manufacturing | 2023 |
| 3KAS Ltd | Wholesale & retail | 2025 |
| 3M Installations Ltd | Administrative & support | 2017 |
| 3M Tints Ltd | Wholesale & retail | 2025 |
| 3MATTER Ltd | Professional & scientific | 2016 |
| 3MS Construction Limited | Construction | 2010 |
| 3N Trading Ltd | Wholesale & retail | 2026 |
| 3N Z Trading Limited | Hospitality | 2019 |
| 3R'S IT Ltd | Information & communication | 2003 |
| 3RD-AI Limited | Information & communication | 2025 |
| 3S Retail Ltd | Wholesale & retail | 2023 |
| 3S XPO & MPO Ltd | Wholesale & retail | 2023 |
| 3SIXFIVE Pro Limited | Professional & scientific | 2019 |
| 3T Bros Limited | Financial services | 1997 |
| 3T Safety and Training Limited | Construction | 2023 |
| 3TOOL.AI Ltd | Professional & scientific | 2025 |
| 3VG Properties Limited | Real estate | 2018 |
| 3XRE Ltd | Professional & scientific | 2024 |
| 4 Cathedral Parc Management Company Limited | Households | 2014 |
| 4 Corners Marine Services Ltd | Manufacturing | 2018 |
| 4 Counties Solutions Ltd | Water & waste | 2019 |
| 4 Football Agency Ltd | Administrative & support | 2019 |
| 4 Home Developments Limited | Real estate | 2025 |
| 4 Iiii Ltd | Information & communication | 2021 |
| 4 Knights Ltd | Arts & recreation | 2005 |
| 4 Lionesses Ltd | Hospitality | 2024 |
| 4 Park Road (Penarth) Management Company Limited | Real estate | 1984 |
| 4 Real Creative Limited | Professional & scientific | 2014 |
| 4 Seasons 4 Ltd | Hospitality | 2019 |
| 4 Seasons Grocery Ltd | Wholesale & retail | 2021 |
| 4 Spheres Limited | Financial services | 2023 |
| 4 Sure Installations Limited | Construction | 2015 |
| 4 Tracks Logistics & Freight Ltd | Transport & logistics | 2019 |
| 4 Winds User LED Association | Health & social care | 1998 |
| 4.Y Service Limited | Transport & logistics | 2024 |
| 40 Beauchamp Street Ltd | Extraterritorial | 2008 |
| 40 Management Limited | Other services | 2015 |
| 40 Station Road Ltd | Real estate | 2014 |
| 404 Entertainment Limited | Hospitality | 2017 |
| 41 Plasturton Gardens Limited | Households | 2021 |
| 41 Velindre Road Limited | Households | 2016 |
| 42 Degrees Coaching Services Limited | Administrative & support | 2014 |
| 42 Llantrisant ST Management Ltd | Households | 2022 |
| 42 Solutions Limited | Information & communication | 2004 |
| 42 to 52 Rookwood Close (Llandaff) Limited | Real estate | 1997 |
| 43 Main Street Limited | Real estate | 2015 |
| 43 Tewksbury Street Limited | Administrative & support | 2014 |
| 44 JIA Ltd | Wholesale & retail | 2021 |
| 44 Rickard Street RTM Company Limited | Households | 2014 |
| 44 Taff Embankment Management Company Limited | Households | 2004 |
| 44LAW Limited | Professional & scientific | 2016 |
| 44RONT Limited | Information & communication | 2017 |
| 44SPORTS Limited | Arts & recreation | 2015 |
| 45 Scientific Ltd | Information & communication | 2017 |
| 45DRIVES UK Ltd | Information & communication | 2025 |