| Inchbrook Trading Estate Management Company Limited | Real estate | 1989 |
| Inclusa Ltd | Information & communication | 2026 |
| Independent Arboriculture & Urban Forestry Ltd | Administrative & support | 2017 |
| Independent Financial Advisor Management Solutions Limited | Information & communication | 2010 |
| Indigo Rail Limited | Information & communication | 2019 |
| Indigo Training Limited | Education | 2010 |
| Industrial Health Consultancy Services LLP | | 2026 |
| Industrial Health Services Ltd | Health & social care | 2023 |
| Ingenuity Services Limited | Information & communication | 2000 |
| Initia Property Developers Ltd | Real estate | 2025 |
| Innovate Twenty One Limited | Professional & scientific | 2021 |
| Inside OUT Decorating Ltd | Construction | 2013 |
| Insight Utility Management Ltd | Professional & scientific | 2024 |
| Insightmentors Ltd | Professional & scientific | 2015 |
| Inspire Design International Limited | Wholesale & retail | 2009 |
| Inspire Heritage Services Ltd | Professional & scientific | 2018 |
| Inspired Skies Limited | Extraterritorial | 2011 |
| Instinct Apparel Ltd | Wholesale & retail | 2020 |
| Insulation Store Limited | Wholesale & retail | 2010 |
| Intelligent Media Limited | Information & communication | 2023 |
| Inter Orbis Limited | Information & communication | 2011 |
| International Event Venues Ltd | Administrative & support | 2016 |
| International Quarrying Consultants Limited | Mining & quarrying | 1967 |
| Intertech Process Machinery Management Limited | Manufacturing | 1991 |
| Intertidal LAB CIC | Education | 2025 |
| Into Nature CIC | Education | 2019 |
| Investments Twenty-Three Ltd | Financial services | 2023 |
| Investor Exchange Ltd | Wholesale & retail | 2025 |
| Involve Solutions Limited | Information & communication | 2008 |
| ION Horse Limited | Manufacturing | 2024 |
| ION LAB Limited | Manufacturing | 2025 |
| Irender Ltd | Construction | 2019 |
| Iron Frog Ltd. | Manufacturing | 2015 |
| Isabelle Walker Productions Ltd | Professional & scientific | 2019 |
| Island Peak Films Limited | Information & communication | 2012 |
| Isle of Noise Limited | Information & communication | 2016 |
| Iswe Foundation Ltd | Professional & scientific | 2018 |
| Italian Auto Moto Club Limited | Arts & recreation | 2009 |
| Ivar Investment and Development Limited | Construction | 2017 |
| IVY on the Wall Interiors Ltd | Manufacturing | 2018 |
| J & L Concrete Pumping Limited | Construction | 2024 |
| J a Rich Solutions Limited | Professional & scientific | 2023 |
| J J'S Taxis (Chippenham) Limited | Transport & logistics | 2007 |
| J Jones and Co Holdings Ltd | Real estate | 2021 |
| J R Mcgill (Construction) Limited | Construction | 1994 |
| J Sparrow Electrical Ltd | Construction | 2017 |
| J Sutton Construction Limited | Construction | 2016 |
| J&C Accounting Services Ltd | Professional & scientific | 2025 |
| J&C Elvin Ltd | Construction | 2019 |
| J&G Holmes Medical Limited | Health & social care | 2019 |
| J&I Trading Limited | Wholesale & retail | 2016 |
| J&W Foil Limited | Other services | 2022 |
| J.A.Gordon & SON Limited | Construction | 1963 |
| J.B. Ward + Sons LLP | | 2014 |
| J.Hall & Son(Bakers)Limited | Manufacturing | 1975 |
| J23 Business Ltd | Other services | 2023 |
| Jacaranda Flowers Ltd | Wholesale & retail | 2013 |
| Jackson Fawkes Ltd | Arts & recreation | 2025 |
| Jacksons Liquid Assets Ltd | Manufacturing | 2018 |
| Jacksons Transport Limited | Transport & logistics | 2000 |
| Jacob Arthur Photography LLP | | 2025 |
| Jacobs Brickwork Ltd | Manufacturing | 2025 |
| Jacome Limited | Real estate | 2010 |
| Jama Homes Ltd | Real estate | 2023 |
| James & Owen Limited | Wholesale & retail | 1926 |
| James Lear of Arundel Limited | Wholesale & retail | 2012 |
| Jammac Care Group Limited | Health & social care | 2018 |
| JAN at Felbrigg Limited | Wholesale & retail | 2013 |
| Jarrot Engines Limited | Wholesale & retail | 2006 |
| Javen Consulting Limited | Professional & scientific | 2005 |
| Jaybee Holdings Ltd | Extraterritorial | 1996 |
| Jaybee Plant Ltd | Extraterritorial | 1996 |
| Jaybee Plant Sales Limited | Wholesale & retail | 1980 |
| JB Optical Ltd | Wholesale & retail | 2021 |
| JB Property Consultants Limited | Professional & scientific | 2024 |
| JC Chiropractic Limited | Health & social care | 2006 |
| JC Motors Cotswolds Ltd | Wholesale & retail | 2023 |
| JC Research Ltd | Professional & scientific | 2025 |
| JDC Creative Services Ltd | Professional & scientific | 2021 |
| JEBRANCH100 Ltd | Financial services | 2025 |
| JEC Norman Ltd | Households | 2025 |
| Jenerick Ltd | Wholesale & retail | 2025 |
| Jenhead Flats Company Limited | Households | 1980 |
| Jerach Technology Ltd | Wholesale & retail | 2023 |
| Jeremy Marchant Limited | Professional & scientific | 2003 |
| Jerobo Homes Limited | Wholesale & retail | 1988 |
| Jessica Draper Equine Limited | Agriculture & fishing | 2025 |
| Jetkas Ltd | Wholesale & retail | 2023 |
| Jewantsum Ltd | Hospitality | 2003 |
| Jewel Hospitality Ltd | Hospitality | 2007 |
| JF Advisory Ltd | Professional & scientific | 2023 |
| JH AMZ Holding Limited | Wholesale & retail | 2023 |
| Jimmy Thompson Creative Ltd | Professional & scientific | 2019 |
| Jims Gym Limited | Arts & recreation | 2023 |
| JJ Development Ltd | Real estate | 2002 |
| JLS Carpentry Ltd | Construction | 2017 |
| JLS Supplies Limited | Wholesale & retail | 2005 |
| JMH Foods Ltd | Manufacturing | 2016 |
| JML Training Ltd | Education | 2014 |
| Jmws Ventures Limited | Wholesale & retail | 2022 |