| Justin Nicholls Ltd | Information & communication | 2012 |
| Justin Pacheco Construction Limited | Construction | 2026 |
| Justinbuild Ltd | Construction | 2019 |
| Justone Theatre Arts C.I.C. | Education | 2014 |
| Justwai Limited | Manufacturing | 2019 |
| Justyol Ltd | Wholesale & retail | 2025 |
| Jutlla Holdings Ltd | Financial services | 2022 |
| Jutta Ltd | Wholesale & retail | 2025 |
| Juvenica Ltd | Wholesale & retail | 2025 |
| Juvista Ltd | Education | 2025 |
| Juvo Resourcing Ltd | Administrative & support | 2015 |
| Juxin Cardiff Limited | Wholesale & retail | 2024 |
| Juxtacon Ltd | Construction | 2018 |
| Juxun Trade Ltd | Wholesale & retail | 2024 |
| Juyin Media Limited | Professional & scientific | 2025 |
| JV International Holdings Ltd | Construction | 2017 |
| JVJ Roofing and Building Ltd | Construction | 2025 |
| JVM Health Ltd | Health & social care | 2024 |
| Jvrsciqa Mart Ltd | Wholesale & retail | 2025 |
| JVW Taverns Ltd | Hospitality | 2025 |
| JW Asset Group Ltd | Financial services | 2026 |
| JW Block Management Limited | Households | 2020 |
| JW Builder Ltd | Construction | 2020 |
| JW Cardiff Limited | Professional & scientific | 2010 |
| JW Fire Safety Solutions Limited | Administrative & support | 2017 |
| JW Partnership (JWP) Limited | Construction | 2018 |
| JW Plastering & Building Services Cardiff Limited | Construction | 2021 |
| JW Sports Media Limited | Information & communication | 2008 |
| JWA Financial Planning Ltd | Financial services | 2016 |
| Jwafp Holdings Ltd | Financial services | 2023 |
| Jwbiz Ltd | Information & communication | 2022 |
| Jwelsh Limited | Health & social care | 2020 |
| JWF Realisations Limited | Manufacturing | 1977 |
| Jwfs Property Limited | Construction | 2023 |
| Jwgm Contracting Limited | Financial services | 2012 |
| Jwhw Finance Ltd | Financial services | 2025 |
| Jwiai Ltd | Information & communication | 2025 |
| Jwjbr Investments Ltd | Real estate | 2019 |
| Jwlc Ltd | Professional & scientific | 2019 |
| JWM Roofing and Property Services Limited | Construction | 2020 |
| Jwqa & Inspection Services Ltd | Construction | 2018 |
| Jwreilly Limited | Professional & scientific | 2025 |
| JWS Coatings UK (Commercial) Ltd | Construction | 2022 |
| JWS Coatings UK (Industrial) Ltd | Construction | 2022 |
| JWS Coatings UK Ltd | Construction | 2019 |
| Jwshomes Ltd | Real estate | 2024 |
| JWT Group Limited | Wholesale & retail | 2019 |
| JXD Consulting Limited | Information & communication | 2008 |
| Jxis Ltd | Information & communication | 2015 |
| JY Stores Ltd | Wholesale & retail | 2024 |
| JY Travel Ltd | Transport & logistics | 2024 |
| JYB Building Services Limited | Wholesale & retail | 2026 |
| Jycey Ltd | Professional & scientific | 2024 |
| Jyloria Ltd | Education | 2025 |
| Jylsxghy Limited | Information & communication | 2021 |
| JYM Well-Being Consultation UK Ltd | Health & social care | 2025 |
| Jyntra Ltd | Education | 2025 |
| Jyuan Ltd | Wholesale & retail | 2025 |
| JZ Transport & Removal Ltd | Transport & logistics | 2022 |
| JZ Ventures Limited | Hospitality | 2018 |
| K $ J Co. Ltd | Wholesale & retail | 2026 |
| K & G Maintenance Limited | Construction | 2017 |
| K & K 100 Ltd | Real estate | 2025 |
| K & M Construction Northwest Ltd | Construction | 2018 |
| K & M Sports Events Limited | Wholesale & retail | 2002 |
| K & R Cheap Services Ltd | Transport & logistics | 2017 |
| K & W Bloodstock Limited | Agriculture & fishing | 2020 |
| K & W Developments (Wales) Limited | Real estate | 2006 |
| K & W Developments Limited | Real estate | 1999 |
| K & W Developments One Limited | Construction | 1999 |
| K & W Property Trading Limited | Real estate | 2004 |
| K a Operations Ltd | Financial services | 2013 |
| K a Store Ltd | Wholesale & retail | 2013 |
| K and E Foods Ltd | Hospitality | 2022 |
| K and P Crabtree Consultancy Ltd | Education | 2019 |
| K Berg Limited | Professional & scientific | 2020 |
| K C Building Designs Ltd | Construction | 2018 |
| K C Construction Leicester Ltd | Construction | 2016 |
| K C Kitchen Fitting Limited | Construction | 2017 |
| K C Smith Roofing and Cladding Limited | Construction | 2020 |
| K E Building Services Ltd | Construction | 2018 |
| K E Building Solutions Ltd | Construction | 2016 |
| K E Realisations Limited | Manufacturing | 1991 |
| K H Business Solutions Ltd | Real estate | 2021 |
| K H Nails 24 Ltd | Other services | 2024 |
| K Henderson Ltd | Other services | 2015 |
| K I Adventurers CIC | Health & social care | 2025 |
| K JAN Limited | Information & communication | 2015 |
| K K Editing Limited | Information & communication | 2017 |
| K L Allcock Ltd | Wholesale & retail | 2025 |
| K M Coaching Limited | Health & social care | 2009 |
| K M Logistics Limited | Transport & logistics | 2016 |
| K Mohanty Ltd | Health & social care | 2008 |
| K Moore Solutions Limited | Water & waste | 2013 |
| K Pepper Construction Limited | Construction | 2025 |
| K Plastics Distribution Limited | Wholesale & retail | 2026 |
| K R Concrete Pumping Ltd | Manufacturing | 2016 |
| K Rentals Ltd | Other services | 2025 |
| K Riley Limited | Construction | 2004 |
| K S Barry (Plumbing, Heating & Renewables) Ltd | Construction | 2002 |