| JLE Selections Ltd | Administrative & support | 2026 |
| JLF Haymer & Sons Limited | Construction | 2009 |
| JLN Construction Limited | Construction | 2020 |
| JLN Contracting Ltd | Construction | 2016 |
| JMB Group (Dowlais) Limited | Professional & scientific | 2011 |
| JME Industrial Services Ltd | Manufacturing | 2026 |
| JMR Innovations Ltd | Wholesale & retail | 2025 |
| JNP Legal Limited | Professional & scientific | 2011 |
| Jo's Beautician Ltd | Other services | 2022 |
| Jodan Contracts Limited | Construction | 2015 |
| JOE Nettle Rail Ltd | Construction | 2025 |
| Joes Events Limited | Hospitality | 2024 |
| Jol's Holdings Limited | Hospitality | 2020 |
| Jonathan Haxton Consulting Ltd | Professional & scientific | 2013 |
| Jones Building Ltd | Construction | 2017 |
| Jones Interiors (South Wales) Ltd | Construction | 2019 |
| JOS Letting Ltd | Real estate | 2022 |
| JP & RH Holdings Ltd | Financial services | 2023 |
| JP Group Asset Holdings Ltd | Financial services | 2024 |
| JPM Developments Ltd | Real estate | 2025 |
| JPW Surfacing Limited | Construction | 2020 |
| JR Holiday Cottages Ltd | Hospitality | 2020 |
| Jude Developments Ltd | Construction | 2026 |
| Jude Lucas Property Ltd | Real estate | 2025 |
| Juggys Plaice Ltd | Hospitality | 2026 |
| Julies Catering Ltd | Hospitality | 2018 |
| Jura Labs CIC | Information & communication | 2026 |
| Justcarpetsuk Limited | Wholesale & retail | 2012 |
| JW & Sons Property's Ltd | Real estate | 2024 |
| JW Grounds Maintenance & Trail Limited | Agriculture & fishing | 2020 |
| Jw&Sons Holdings Ltd | Financial services | 2025 |
| JWD Construction Limited | Construction | 2016 |
| Jzrw Limited | Extraterritorial | 2024 |
| K & D Crandon & SON Ltd | Other services | 2025 |
| K Davis Services Limited | Manufacturing | 2016 |
| K&T Retail Store Ltd | Wholesale & retail | 2025 |
| K&W Holiday Lets Ltd | Real estate | 2025 |
| K.S.Regan Electrical Limited | Construction | 2017 |
| Kaagrace Limited | Construction | 2014 |
| Kaiden Williams Trading Limited | Hospitality | 2023 |
| Kamwah Point Ltd | Hospitality | 2025 |
| Kaneschar Store Ltd | Wholesale & retail | 2025 |
| Karen Blake Coaching Limited | Administrative & support | 2017 |
| Karim Wales Developments Ltd | Administrative & support | 2023 |
| Karl Jones Plumbing & Heating Services Limited | Construction | 2004 |
| Katu Commercial Services Ltd | Administrative & support | 2019 |
| Kaykel Communications Limited | Information & communication | 2009 |
| KCA Facilities Limited | Real estate | 2025 |
| KDR Property Holdings Limited | Real estate | 2017 |
| Kdswasteservices Ltd | Water & waste | 2026 |
| Kebab Zone Ltd | Hospitality | 2024 |
| Kecw Group Limited | Professional & scientific | 2016 |
| Kelray Ltd | Construction | 1998 |
| KEN Bateman Surveying Ltd | Professional & scientific | 2021 |
| Kendry Commercial Cleaning Limited | Administrative & support | 2025 |
| Kerbside ADS Limited | Administrative & support | 2014 |
| Key Health Nutrients Limited | Health & social care | 2021 |
| Key Health Therapies Limited | Administrative & support | 2024 |
| Key Mortgage & Financial Advice Ltd | Financial services | 2013 |
| KEYS4SUCCESS Ltd | Education | 2018 |
| Keyvapour Properties Ltd | Wholesale & retail | 2023 |
| Keyvapours Limited | Wholesale & retail | 2014 |
| Kgem Developments Limited | Construction | 2023 |
| KHCASTLE2022 Ltd | Real estate | 2022 |
| Khehra Enterprise 5 Ltd | Hospitality | 2021 |
| Khehra Enterprise 6 Ltd | Hospitality | 2021 |
| Khehra Enterprise Ltd | Hospitality | 2014 |
| KHN Consultancy Limited | Professional & scientific | 2020 |
| Kian Property Management Limited | Real estate | 2021 |
| KJR Services (UK) Ltd | Construction | 2014 |
| KJS Logistics Ltd | Transport & logistics | 2023 |
| KK Party Play CYF | Agriculture & fishing | 2020 |
| KLA Medical Limited | Health & social care | 2023 |
| KLC 28 Limited | Hospitality | 2009 |
| KLR (Services) Ltd | Construction | 2014 |
| KN Barber Ltd | Other services | 2025 |
| Knoyle Phillips Ltd | Professional & scientific | 2022 |
| Kooler X Limited | Hospitality | 2023 |
| KP Quality Roofing Limited | Construction | 2025 |
| Kram Initiative Limited | Professional & scientific | 2020 |
| KRJ Enterprises Ltd | Transport & logistics | 2026 |
| KSA Medical Limited | Other services | 2024 |
| Kudos Fundraising Ltd | Professional & scientific | 2020 |
| Kurd Halal Ltd | Wholesale & retail | 2023 |
| L & a Estates Ltd | Households | 2024 |
| L a J Health & Fitness Ltd | Other services | 2026 |
| L J Railtech Limited | Construction | 2019 |
| L Murphy Plumbing & GAS Services Ltd | Construction | 2024 |
| L&R Building & Roofing Ltd | Construction | 2022 |
| L.G.&B. Limited | Hospitality | 2011 |
| L16MRAIL Ltd | Construction | 2014 |
| LA Bocata Ltd | Hospitality | 2025 |
| LA Psychology Limited | Health & social care | 2025 |
| Ladybirds Hair Centre Limited | Other services | 2009 |
| Lake District Homes & Lettings Limited | Construction | 2022 |
| Langdale Cottages Ltd | Real estate | 2023 |
| Laserase Wales Limited | Other services | 2024 |
| Launch FLY Capture Technologies Ltd | Construction | 2018 |
| Laundry Lounge 01 Ltd | Administrative & support | 2026 |
| Laura Evans Coaching & Mentoring Limited | Professional & scientific | 2020 |