| JIO Sims Holdings Ltd | Real estate | 2026 |
| JJ Collectables Ltd | Wholesale & retail | 2025 |
| Jjas Properties Ltd | Real estate | 2019 |
| JJK Express Limited | Wholesale & retail | 2023 |
| JK Quality Homes Ltd | Real estate | 2025 |
| JK Smart Logistics Ltd | Wholesale & retail | 2024 |
| Jkmo Transport Ltd | Transport & logistics | 2021 |
| Jkndistributions Ltd | Wholesale & retail | 2026 |
| JLC Carpentry Ltd | Other services | 2018 |
| Jlha Ltd | Real estate | 2020 |
| JLP Property Estates Limited | Real estate | 2026 |
| JLR Construction Group Limited | Construction | 2025 |
| JM Landscape Architecture Ltd | Professional & scientific | 2025 |
| JM Perfect Build Limited | Construction | 2009 |
| JMC Property Consultancy Limited | Information & communication | 2025 |
| JMG Corporate Services Ltd | Professional & scientific | 2017 |
| JMP Electrical Ltd | Administrative & support | 2016 |
| JMV Builders Limited | Manufacturing | 2025 |
| JNC Consulting Ltd | Construction | 2023 |
| JNT Commercial Limited | Administrative & support | 2019 |
| Joba Properties Limited | Real estate | 2017 |
| JOE & B Ltd | Transport & logistics | 2020 |
| JOE Flemons Ltd | Information & communication | 2018 |
| Joedah Limited | Other services | 2025 |
| John Frances (Contracts) Limited | Construction | 2020 |
| John Goose Limited | Transport & logistics | 2026 |
| John Holtom Consultancy Limited | Professional & scientific | 2019 |
| John Walton Consultancy Ltd | Information & communication | 2005 |
| Johnsmith Investments Ltd | Hospitality | 2024 |
| Johnson Tamara Limited | Manufacturing | 2014 |
| Johnston Property Development Ltd | Construction | 2025 |
| Joinspan Property Management Limited | Real estate | 1990 |
| Jolab International Limited | Transport & logistics | 2018 |
| JON DUN Limited | Health & social care | 2009 |
| Jonathan Furse Design Limited | Information & communication | 2023 |
| Jonilar Associates Ltd | Wholesale & retail | 2014 |
| Jonquil Floral Design Ltd. | Wholesale & retail | 2013 |
| Josan Carpentry and Construction Limited | Construction | 2022 |
| Josephine Scott Ltd | Wholesale & retail | 2022 |
| Joshi Electronics Limited | Wholesale & retail | 2025 |
| Josruth Limited | Real estate | 2017 |
| Joy Autos Limited | Wholesale & retail | 2020 |
| Joy Freights Ltd | Transport & logistics | 2025 |
| JP Automotive Services Ltd | Wholesale & retail | 2022 |
| JP Training and Education Limited | Education | 2021 |
| Jp.Un Limited | Financial services | 2018 |
| JPG PAY Weekly Cars Limited | Wholesale & retail | 2018 |
| JPI Automotive & Industrial Limited | Wholesale & retail | 2019 |
| JPL Pubs Ltd | Hospitality | 2023 |
| JPR Electronics Limited | Wholesale & retail | 1979 |
| JS Cartrefi Limited | Real estate | 2024 |
| JS Coaches Ltd | Other services | 2025 |
| JS Studio Ltd | Wholesale & retail | 2020 |
| JS Wolf Ltd | Administrative & support | 2025 |
| Js&Pg Enterprises Ltd | Wholesale & retail | 2026 |
| JSC Treats Ltd | Wholesale & retail | 2021 |
| JSE Services Ltd | Construction | 2023 |
| JSK Design and Build Ltd | Construction | 2025 |
| JSP Foods and Party Ltd | Hospitality | 2023 |
| JT United Limited | Construction | 2023 |
| JTA Domestic Appliance Repairs Ltd | Other services | 2021 |
| Jude Lettings Limited | Real estate | 2018 |
| Juice Shack Limited | Hospitality | 2013 |
| Julia Ltd | Transport & logistics | 2011 |
| Julia Property Ltd | Real estate | 2024 |
| Jumbled Limited | Wholesale & retail | 2023 |
| Jumbo Chinese Takeaway Ltd | Hospitality | 2025 |
| Jumnaz Limited | Transport & logistics | 2020 |
| Junction 93 Limited | Households | 2016 |
| Junior Sporting Academy Ltd | Arts & recreation | 2023 |
| Jury's Investment Limited | Health & social care | 2022 |
| Just a LAB Academy Ltd | Education | 2026 |
| Just Better Education Ltd | Education | 2020 |
| Just Go Limited | Extraterritorial | 2004 |
| Jvst Limited | Transport & logistics | 2013 |
| JW Construction (UK) Limited | Construction | 2008 |
| JW Contracting and Consulting Ltd | Information & communication | 2025 |
| JZ Building Services 23 Ltd | Construction | 2026 |
| K & J Plumbing Limited | Construction | 2005 |
| K ALI Law Limited | Professional & scientific | 2025 |
| K C Engineering (Harpenden) Limited | Manufacturing | 2019 |
| K C S Limited | Extraterritorial | 2004 |
| K DOT Limited | Real estate | 2026 |
| K N Q Properties Ltd | Real estate | 2021 |
| K W Motors Ltd | Wholesale & retail | 2017 |
| K&B Property Developments Ltd | Real estate | 2023 |
| K&M Rusinek Ltd | Construction | 2021 |
| K&M Support Services Ltd | Administrative & support | 2025 |
| K&N Ride Solutions Ltd | Transport & logistics | 2025 |
| K.James Investments Ltd | Real estate | 2018 |
| K.M Carpentry & Joinery Limited | Construction | 2006 |
| K87 Solutions Limited | Administrative & support | 2025 |
| K9 Securex Ltd | Administrative & support | 2026 |
| K9AS Events Ltd | Arts & recreation | 2020 |
| Kaely's Doggy Hotel Limited | Other services | 2015 |
| Kahvi Roast Ltd | Wholesale & retail | 2020 |
| Kailash Investment Properties Ltd | Real estate | 2023 |
| KAJ Trans Ltd | Transport & logistics | 2021 |
| Kaledan Properties Ltd | Real estate | 2017 |
| Kaleidoscope at Dunstable Management Company Limited | Households | 2015 |