| Island Projects Management Ltd | Construction | 2022 |
| Istanbul Homes Limited | Real estate | 2018 |
| IT Cloud Cover Ltd | Information & communication | 2022 |
| It's a Wrap (Andover) Limited | Wholesale & retail | 2016 |
| It's Something Good Limited | Professional & scientific | 2023 |
| IVI 1 Ltd | Construction | 2015 |
| IXL Couriers Ltd | Transport & logistics | 2013 |
| J Aubin Limited | Professional & scientific | 2003 |
| J B Countrywide Ltd | Transport & logistics | 2019 |
| J David Brickwork Limited | Construction | 2017 |
| J P Motors (Christchurch) Limited | Manufacturing | 2007 |
| J T D Construction (Southern) Limited | Construction | 2009 |
| J&J Tiling Ltd | Construction | 2012 |
| J-Load Ltd | Transport & logistics | 2011 |
| J.B Bricklaying & Alterations Limited | Construction | 2018 |
| J.J.G Life Doctor Ltd | Health & social care | 2021 |
| J.T.Ash Technical Ltd | Manufacturing | 2023 |
| JAB Advisory Services Ltd | Financial services | 2016 |
| JAC Property Holdings Ltd | Real estate | 2025 |
| Jackson & Maine Homes Ltd | Administrative & support | 2024 |
| Jacobson Grace Ltd | Real estate | 2013 |
| Jacquard Risk Management Ltd | Administrative & support | 2024 |
| Jacquard Tailoring Ltd | Wholesale & retail | 2024 |
| Jade Road Consulting Limited | Administrative & support | 2026 |
| Jakco Limited | Manufacturing | 2007 |
| Jamcom Development Ltd | Professional & scientific | 2025 |
| James Booth Design & Art Direction Ltd | Professional & scientific | 2023 |
| James Golding Ltd | Other services | 2020 |
| James Groundworks Limited | Construction | 2013 |
| James Lavis Property Services Ltd | Administrative & support | 2023 |
| Jane Fereday Ltd | Professional & scientific | 2021 |
| Jare Airline Training Partnership Limited | Manufacturing | 2004 |
| Java Consultants Limited | Professional & scientific | 2013 |
| JAY Marine Engineering Services Limited | Professional & scientific | 2019 |
| Jaymark Properties Limited | Real estate | 2024 |
| Jaysy Tools Limited | Wholesale & retail | 2016 |
| Jazz Real Estate Limited | Real estate | 2025 |
| JB Decorating & Property Maintenance Ltd | Construction | 2019 |
| JB Maintenance and Renovation Ltd | Construction | 2014 |
| JC Etheridge Construction Ltd | Construction | 2023 |
| JC Fire Maintenance Ltd | Public administration | 2021 |
| JC Rail (Consultancy) Ltd | Professional & scientific | 2026 |
| JC Sports Development Ltd | Education | 2022 |
| JD Garage Dorset Limited | Wholesale & retail | 2016 |
| JDC Property Solutions Ltd | Construction | 2024 |
| JDC Renovations Ltd | Construction | 2025 |
| Jdee Morgan Limited | Real estate | 2025 |
| JDL Trading Dorset Ltd | Real estate | 2014 |
| Jellicoe Stores Ltd | Wholesale & retail | 2012 |
| Jelz Boutique Ltd | Wholesale & retail | 2025 |
| Jemmaco Limited | Manufacturing | 2015 |
| Jenkyn Holdings Limited | Financial services | 2024 |
| Jerrard Keats & Wolley Limited | Real estate | 2003 |
| JET Professional Plumbing & Heating Ltd | Construction | 2026 |
| Jetfly Aviation UK Ltd | Transport & logistics | 2009 |
| JG Transport Consulting Ltd | Other services | 2017 |
| Jgwn Limited | Transport & logistics | 2010 |
| Jhom Homes Ltd | Real estate | 2021 |
| JK Upholstery Ltd | Other services | 2019 |
| JKC Travel Management Ltd | Administrative & support | 2012 |
| JL 941 Limited | Information & communication | 2022 |
| JM Secretarial Services Ltd | Administrative & support | 2025 |
| Jmdt Limited | Arts & recreation | 2007 |
| JMH Financial Services (London) Limited | Professional & scientific | 2012 |
| Joanna's Kitchen Ltd | Hospitality | 2025 |
| Jogo DO Bicho Ltd | Information & communication | 2026 |
| John Foster (Media Promotions) Limited | Professional & scientific | 2000 |
| John Reid & Sons (Strucsteel) Holdings Limited | Manufacturing | 2007 |
| Jonathan Dyer Limited | Health & social care | 2013 |
| Jordan Launder Ltd | Professional & scientific | 2026 |
| Joyce&Sons Ltd | Construction | 2026 |
| JPL Garage Trading Ltd | Wholesale & retail | 2022 |
| JPM Holdings Ltd | Real estate | 2023 |
| JR & Associates Limited | Professional & scientific | 2002 |
| Jsjpm Automation Limited | Professional & scientific | 2023 |
| Juniper Redley Limited | Professional & scientific | 2026 |
| Jurassic Resin Kent Limited | Administrative & support | 2025 |
| Just Fireplaces Limited | Wholesale & retail | 1985 |
| Justgood Group Limited | Wholesale & retail | 2024 |
| JVS Medical Limited | Manufacturing | 2020 |
| JVS Products Limited | Manufacturing | 2012 |
| JW Fire & Security Ltd | Administrative & support | 2021 |
| JWJ Marine Ltd | Manufacturing | 2022 |
| K & B Estates Limited | Construction | 2001 |
| K 5 Barbers Ltd | Other services | 2026 |
| K L Aviation Limited | Wholesale & retail | 1992 |
| K M J Home Improvements Ltd | Professional & scientific | 2023 |
| K&C Partners Ltd | Real estate | 2014 |
| K-Secure Limited | Professional & scientific | 2020 |
| KA Aesthetics Ltd | Other services | 2021 |
| Kall Climate Ltd | Construction | 2026 |
| Kalto Building Services Ltd | Construction | 2026 |
| Karen Baker Limited | Administrative & support | 2014 |
| Kasacod Limited | Hospitality | 2019 |
| Kashmir Dining Ltd | Hospitality | 2019 |
| Katalytik Limited | Professional & scientific | 2004 |
| Kate Howe Limited | Wholesale & retail | 2012 |
| Kato HR Limited | Administrative & support | 2017 |
| Katy TIZ Ltd | Arts & recreation | 2021 |
| KC6067 Studios Ltd | Information & communication | 2025 |