| JAY Spray Ltd | Construction | 2025 |
| Jay-Integrity UK Ltd | Health & social care | 2019 |
| Jayash Limited | Transport & logistics | 2015 |
| Jayco Plumbing & Heating Limited | Construction | 2025 |
| Jayd Investments Ltd | Real estate | 2014 |
| Jayden and Jamie Transport Ltd | Transport & logistics | 2025 |
| Jayden Property Limited | Real estate | 2025 |
| Jayeeta Pharm Limited | Professional & scientific | 2017 |
| Jayford Retail Ltd | Wholesale & retail | 2021 |
| Jayford Two Ltd | Wholesale & retail | 2025 |
| Jayforge Limited | Professional & scientific | 2018 |
| Jayfs Trading Ltd | Wholesale & retail | 2023 |
| Jayko Mortgage Services Limited | Financial services | 2024 |
| Jays Studio Limited | Wholesale & retail | 2015 |
| Jayygoo Ltd | Wholesale & retail | 2026 |
| Jaza Maison Limited | Real estate | 2024 |
| Jaza Services Ltd | Real estate | 2026 |
| Jazz Courier Service Ltd | Transport & logistics | 2020 |
| Jazzcotech CIC | Health & social care | 2023 |
| JB & LD Properties Ltd | Real estate | 2023 |
| JB Construction (Luton) Limited | Construction | 2020 |
| JB Education Consortium Ltd | Administrative & support | 2024 |
| JB Globe Travel Ltd | Administrative & support | 2013 |
| JB Logistics Luton Limited | Transport & logistics | 2025 |
| JB MTA Ltd | Wholesale & retail | 2026 |
| JB Properties Luton Ltd | Real estate | 2022 |
| JB World Ltd | Construction | 2014 |
| JBL Transport Ltd | Transport & logistics | 2014 |
| Jboats Limited | Wholesale & retail | 2024 |
| Jbracing Limited | Arts & recreation | 2023 |
| Jbraz Limited | Manufacturing | 2021 |
| JC Family Holdings Limited | Financial services | 2023 |
| JC Park Homes Ltd | Real estate | 2025 |
| JCB Autos Limited | Wholesale & retail | 2023 |
| JCF Developments Limited | Construction | 2015 |
| Jcranesrtb Ltd | Manufacturing | 2026 |
| JCS Building & Landscapes Ltd | Administrative & support | 2025 |
| JCT 11 Records Ltd | Information & communication | 2026 |
| JCV Electrical Limited | Construction | 2025 |
| JD Mighty Trading Limited | Information & communication | 2024 |
| JD Paving & Drainage Ltd | Construction | 2024 |
| JD Trends Limited | Wholesale & retail | 2026 |
| Jdov Properties Limited | Real estate | 2026 |
| JDP Security Ltd | Construction | 2021 |
| Jdsn Ltd | Wholesale & retail | 2025 |
| Jean Abreu Dance Ltd | Arts & recreation | 2009 |
| Jean City Luton Ltd | Wholesale & retail | 2023 |
| Jean DE LA Claude Limited | Wholesale & retail | 2016 |
| Jebroanz Limited | Wholesale & retail | 2022 |
| Jecklesmiles Ltd | Health & social care | 2020 |
| Jeecode Ltd | Information & communication | 2025 |
| Jeff Lushaj Landscaping Ltd | Construction | 2023 |
| Jeff Production Services Ltd | Hospitality | 2022 |
| JEFF5 Ltd | Real estate | 2019 |
| JEH Electricals Ltd | Construction | 2019 |
| Jehji 247 Limited | Health & social care | 2022 |
| Jemat Heating (Domestic) Limited | Construction | 1981 |
| JEN Capital Limited | Construction | 2023 |
| JEN M Limited | Health & social care | 2023 |
| Jenny Lyons Employability Consultant Limited | Administrative & support | 2020 |
| JEQ Integrated Services Ltd | Construction | 2026 |
| JER Saas CFO Ltd | Professional & scientific | 2023 |
| Jerk & Peri Peri Ltd | Hospitality | 2015 |
| Jerk Box Cuisine Ltd | Hospitality | 2020 |
| Jermaine Amoah Ltd | Information & communication | 2018 |
| Jersycart Limited | Wholesale & retail | 2025 |
| Jess Group Limited | Hospitality | 2026 |
| Jestra Ltd | Wholesale & retail | 2025 |
| Jetaa Itech Ltd | Wholesale & retail | 2025 |
| Jetayu Logistics Limited | Transport & logistics | 2026 |
| Jetset Group Holding (Brazil) Limited | Professional & scientific | 2003 |
| Jetset Group Holding Limited | Administrative & support | 2004 |
| Jettycare Service Ltd | Health & social care | 2026 |
| Jeunepato Limited | Hospitality | 2020 |
| Jewel Pools Ltd | Administrative & support | 2021 |
| Jewelous Limited | Wholesale & retail | 2022 |
| Jewels Autos Ltd | Wholesale & retail | 2016 |
| Jewels by Nazish Limited | Wholesale & retail | 2018 |
| Jewels Estates Ltd | Real estate | 2025 |
| JEY Executive Chuaffer Ltd | Transport & logistics | 2020 |
| Jeylanis Ltd | Information & communication | 2020 |
| JF Flavour Limited | Hospitality | 2025 |
| JF Latif Ltd | Financial services | 2025 |
| JG - CS Investment Ltd | Real estate | 2023 |
| JG Statutory Inspection Services Ltd | Professional & scientific | 2017 |
| JG Tapers & Jointers Ltd | Construction | 2025 |
| Jg&S Services Limited | Wholesale & retail | 2024 |
| JH Brickwork Construction Ltd | Construction | 2024 |
| JH Distribution Ltd | Wholesale & retail | 2026 |
| Jhbv Ltd | Wholesale & retail | 2021 |
| JHO Consulting Ltd | Professional & scientific | 2026 |
| JHS Cars Limited | Administrative & support | 2015 |
| JI Consulting Services Ltd | Other services | 2024 |
| JI International Limited | Financial services | 2020 |
| JI Wholesales Limited | Wholesale & retail | 2021 |
| Ji&Sonlogistics Ltd | Transport & logistics | 2025 |
| Jiang Shan 888 Company Ltd | Hospitality | 2024 |
| Jiant Ltd | Information & communication | 2025 |
| Jibbs IT Consultancy Ltd | Administrative & support | 2017 |
| Jibe Ltd | Wholesale & retail | 2025 |