| Inhouseout Ltd | Manufacturing | 2025 |
| INK Corby Limited | Wholesale & retail | 2024 |
| Inkspire Publishing House Ltd | Information & communication | 2025 |
| Innovate Construction and Renovations Limited | Construction | 2025 |
| Innovate Health Group Ltd | Information & communication | 2019 |
| Innovate Physiotherapy Ltd | Health & social care | 2022 |
| Inovate Logistics Ltd | Transport & logistics | 2019 |
| INQ Ltd. | Information & communication | 2014 |
| Insert Engineering Ltd | Professional & scientific | 2019 |
| Inside OUT Rennovations Limited | Administrative & support | 2023 |
| Insignia Holdings Limited | Professional & scientific | 2009 |
| Insignia Manufacturing Limited | Manufacturing | 2009 |
| Insignia PM Limited | Real estate | 2019 |
| Inspired Surfaces Limited | Manufacturing | 2010 |
| Insport Group Ltd | Health & social care | 2025 |
| Instafresh Ltd | Wholesale & retail | 2021 |
| Instafresh Scents Ltd | Wholesale & retail | 2024 |
| Inta-Lock Locksmiths Ltd | Administrative & support | 2018 |
| Intact Logistics Ltd | Transport & logistics | 2025 |
| Integrated Land Management Ltd | Professional & scientific | 2020 |
| Integrated Services (N) Limited | Other services | 2017 |
| Intelect Auto Ltd | Real estate | 2016 |
| Intelliconnect (Europe) Limited | Manufacturing | 2005 |
| Intelligent Services PVT Ltd | Transport & logistics | 2023 |
| Intelligent Steel Construction Limited | Construction | 2013 |
| Inter Express Transport Ltd | Transport & logistics | 2025 |
| Interact Analysis Group Holdings Limited | Financial services | 2017 |
| Interact Analysis UK Limited | Information & communication | 2017 |
| Interkey Contracting Ltd | Construction | 2018 |
| Interkey Properties Limited | Construction | 2025 |
| International Express Services Limited | Transport & logistics | 2024 |
| Internet of Printing UK Limited | Information & communication | 2018 |
| Intrinsic Systems Ltd | Information & communication | 2002 |
| Ioan Cristian Ltd | Wholesale & retail | 2017 |
| Ioan&Ana Ltd | Transport & logistics | 2022 |
| ION Mitu Ltd | Transport & logistics | 2016 |
| Ionut a Antonica Ltd | Construction | 2024 |
| Iota Interiors Limited | Wholesale & retail | 2019 |
| Ipadea Limited | Water & waste | 2021 |
| Irish Wolfhound UK Northamptonshire Ltd | Agriculture & fishing | 2026 |
| Irku Property Management Ltd | Real estate | 2025 |
| Isabelle and George Fine Watches Limited | Wholesale & retail | 2024 |
| Isaraden Limited | Construction | 2026 |
| Ischus Healthcare Services Ltd | Health & social care | 2014 |
| Islejoux Ltd | Wholesale & retail | 2026 |
| ISM Academy Education Limited | Education | 2018 |
| ISM Academy Limited | Other services | 2013 |
| ISM Holiday Clubs Limited | Education | 2023 |
| Ismael Barazar Recruitment Limited | Hospitality | 2023 |
| ISO Energy Solar Limited | Administrative & support | 2011 |
| Istvan Farkas Ltd | Transport & logistics | 2014 |
| Isunas Consultancy Limited | Professional & scientific | 2019 |
| IT Daddy Limited | Information & communication | 2024 |
| IT Recruitment UK Limited | Administrative & support | 2024 |
| Itmo Future Innovation Limited | Information & communication | 2025 |
| Itstorm Ltd | Information & communication | 2005 |
| Itucci Ltd | Wholesale & retail | 2019 |
| Iustin MST Ltd | Transport & logistics | 2026 |
| IVY Rosewood Care Limited | Health & social care | 2026 |
| Ivy's Luxury Homes Limited | Professional & scientific | 2023 |
| IY Commissioning Limited | Professional & scientific | 2018 |
| IY Enterprises Ltd | Arts & recreation | 2023 |
| IY Group Limited | Financial services | 2025 |
| Izzy Ride Transport Limited | Transport & logistics | 2026 |
| J & a Young (Holdings) Limited | Water & waste | 2001 |
| J & a Young (Racing) Limited | Administrative & support | 1990 |
| J & a Young Group Limited | Other services | 2008 |
| J and L Northants Ltd | Real estate | 2024 |
| J B Pipe Services Limited | Professional & scientific | 2020 |
| J D Nikomen Limited | Wholesale & retail | 2012 |
| J Harris Ltd | Real estate | 2012 |
| J M Mcgill Ltd. | Wholesale & retail | 2002 |
| J R Property Lets Ltd | Extraterritorial | 2024 |
| J Ruddick Ltd | Transport & logistics | 2023 |
| J W S Boiler Installations Limited | Construction | 2022 |
| J Wells Engineering Limited | Professional & scientific | 2026 |
| J Wilkes Ltd | Information & communication | 2015 |
| J&G Property (SPV) Ltd | Real estate | 2026 |
| J&R Car Service Ltd | Wholesale & retail | 2021 |
| J. and a. Young (Leicester) Limited | Wholesale & retail | 1975 |
| J.C's Noble-Innovations Ltd | Professional & scientific | 2017 |
| J.M.W Electrical Ltd | Construction | 2016 |
| Jaan Services Limited | Health & social care | 2017 |
| JAB Composites Ltd | Professional & scientific | 2016 |
| Jabary Properties Ltd | Real estate | 2023 |
| Jack & Sons Ltd | Transport & logistics | 2012 |
| Jack Nolan Carpentry Limited | Extraterritorial | 2022 |
| Jackho Group EOT Limited | Financial services | 2025 |
| Jackho Limited | Financial services | 2017 |
| Jackho Propco Ltd | Real estate | 2019 |
| James & Young Ltd | Professional & scientific | 2021 |
| James Connolly Wholesale Limited | Manufacturing | 1986 |
| James Patrick Limited | Information & communication | 1996 |
| Jamieson Property Limited | Real estate | 2019 |
| Jampth Limited | Information & communication | 2017 |
| Jandy Driving Services Ltd | Transport & logistics | 2023 |
| Janica Escoro Recruitment Limited | Administrative & support | 2022 |
| Jankop Carpentry & Joinery Ltd | Construction | 2018 |
| Janthian Limited | Administrative & support | 2026 |
| Jaro Panels Limited | Manufacturing | 2014 |