| Impulse Performance Ltd | Education | 2026 |
| IN Your Corner Business Support Ltd | Administrative & support | 2026 |
| Incal Consulting Limited | Professional & scientific | 2017 |
| Incident Sync Ltd | Financial services | 2026 |
| Inclusion East CIC | Information & communication | 2011 |
| Incorporated Bishop's Stortford College Association(The) | Education | 1904 |
| Indigo Culture Limited | Wholesale & retail | 2021 |
| Indrila Ltd | Professional & scientific | 2014 |
| Indulgence Bidco Limited | Financial services | 2021 |
| Indulgence Debtco Limited | Financial services | 2021 |
| Indulgence Midco Limited | Financial services | 2021 |
| Indulgence Newco Limited | Financial services | 2021 |
| Industrial Spraying Services Herts Ltd | Construction | 2025 |
| Infinite Shelf Ltd | Wholesale & retail | 2026 |
| Infinity Bikes Ltd | Wholesale & retail | 2021 |
| Infoorbit Technologies Ltd | Information & communication | 2022 |
| Informaticsco Ltd | Information & communication | 2023 |
| Infratech Academy Limited | Information & communication | 2025 |
| Ingenium Properties Ltd | Real estate | 2018 |
| Innervision Design Ltd | Professional & scientific | 2013 |
| INNOV8 Security Ltd | Administrative & support | 2010 |
| Innovation House Management Limited | Households | 2016 |
| Innovation With Energy CIC | Information & communication | 2026 |
| Innpact Ltd | Professional & scientific | 2019 |
| Insightment Coaching Ltd | Education | 2018 |
| Inspire Stays Ltd | Administrative & support | 2022 |
| Inspired by Compliments Ltd | Wholesale & retail | 2014 |
| Integrate Group Ltd | Manufacturing | 2017 |
| Integrated Admin Solutions Ltd | Administrative & support | 2022 |
| Integrity Partners Limited | Information & communication | 2014 |
| Integrum Building Services Ltd | Construction | 2020 |
| Intensivecourses.Co.Uk Limited | Education | 2007 |
| Interim Management Projects Limited | Professional & scientific | 2023 |
| Inveniam Consortium Ltd | Information & communication | 1991 |
| Investor Compensation Limited | Administrative & support | 2003 |
| Ipsum Building Services Limited | Professional & scientific | 2016 |
| Ipsum Engineering Ltd | Construction | 2014 |
| Irellimac Ltd | Real estate | 2022 |
| Irene & Cecile Ltd | Professional & scientific | 2016 |
| Iridium Designs Ltd | Information & communication | 2011 |
| Iron Duke Productions Ltd | Information & communication | 2024 |
| Irwell Trade Limited | Administrative & support | 2025 |
| Isabel Hall Ltd | Other services | 2021 |
| Ishita RC Ltd | Professional & scientific | 2024 |
| Iskippy Golf Co. Ltd | Arts & recreation | 2025 |
| Ismael Munir Ltd | Information & communication | 2025 |
| Ispire MC Ltd | Health & social care | 2017 |
| IT Data Consultants Limited | Information & communication | 2023 |
| It's OK NOT to BE OK Ltd | Health & social care | 2020 |
| Italian Stone Trading Ltd | Professional & scientific | 2019 |
| Iteam Ltd | Professional & scientific | 2024 |
| Iteron Holding Limited | Administrative & support | 2014 |
| Itgmedia Limited | Information & communication | 2017 |
| Itslivenow Limited | Information & communication | 2018 |
| Itvet Group Limited | Financial services | 2023 |
| Itvet Limited | Information & communication | 2007 |
| IVY Cottage Property Investments Ltd | Real estate | 2025 |
| IZN Limited | Wholesale & retail | 2012 |
| Izod Limited | Extraterritorial | 1999 |
| J & H Environmental Design Ltd | Professional & scientific | 2021 |
| J a B Business Services Limited | Administrative & support | 2003 |
| J C Security Installations Limited | Administrative & support | 2013 |
| J Davies Ltd | Construction | 2021 |
| J Day & SON (Holdings) Limited | Administrative & support | 2009 |
| J Day & SON Limited | Manufacturing | 1965 |
| J Downey Ltd | Professional & scientific | 2026 |
| J E Knight Building Services Ltd | Construction | 2022 |
| J Hunt Financial Services Limited | Financial services | 2020 |
| J More Building Services Limited | Construction | 2015 |
| J Murray Research & Consulting Ltd | Professional & scientific | 2023 |
| J S Motion Pictures Ltd | Information & communication | 2023 |
| J Stacey Electrical Limited | Construction | 2009 |
| J W Llande Ltd | Information & communication | 2015 |
| J&B Partners Limited | Professional & scientific | 2010 |
| J&Co Construction Ltd | Construction | 2025 |
| J&S Speedy Van Ltd | Transport & logistics | 2012 |
| J-R Brothers Haulage Limited | Transport & logistics | 2020 |
| J. Dixon Accountants Limited | Real estate | 2010 |
| J.Gleancoaching Ltd | Other services | 2023 |
| J.H Farms LLP | | 2009 |
| J.P.L. Interiors and Doorsets Limited | Administrative & support | 2005 |
| J.R.J. Holdings Liverpool Limited | Administrative & support | 1973 |
| J.R.Stone Construction Limited | Construction | 2018 |
| J.S.Garton & SON Limited | Agriculture & fishing | 1963 |
| J.T.B Construction Ltd | Construction | 2023 |
| J5 Interiors Limited | Manufacturing | 2018 |
| Jaali Limited | Professional & scientific | 2011 |
| JAB Media Solutions Ltd | Information & communication | 2016 |
| Jacaranda Trading Limited | Professional & scientific | 2006 |
| Jacks Contractors Ltd | Construction | 2025 |
| Jade Leigh Parr Limited | Arts & recreation | 2023 |
| Jade Pearl Ltd | Wholesale & retail | 2021 |
| Jades Thorley Limited | Hospitality | 2024 |
| JAH Ventures Ltd | Professional & scientific | 2023 |
| Jaimee Sydney Ltd | Professional & scientific | 2021 |
| Jais Manufacturing Ltd | Manufacturing | 2025 |
| Jake's Chilli JAM Limited | Manufacturing | 2022 |
| Jallow Properties Ltd | Real estate | 2020 |
| JAM Batch Ltd | Manufacturing | 2018 |
| Jamel Holding Limited | Financial services | 2025 |