| Ink:D Properties Ltd | Real estate | 2014 |
| Inner Connect Ltd | Information & communication | 2024 |
| Innovative Accounting Limited | Administrative & support | 2014 |
| Innovative Enterprise Solutions Limited | Information & communication | 1998 |
| INNOVATIVE8 Limited | Manufacturing | 2019 |
| Innovia Services Limited | Professional & scientific | 1996 |
| Innovo Landscapes Limited | Administrative & support | 2025 |
| Inovo Robotics Ltd | Manufacturing | 2016 |
| Insidestore Ltd | Wholesale & retail | 2011 |
| Insight Opticians Frimley Limited | Health & social care | 2002 |
| Inspectrum Food Safety Limited | Hospitality | 2022 |
| Inspiration Events Limited | Professional & scientific | 2011 |
| Inspire Girls Academy Ltd | Arts & recreation | 2024 |
| Inspire Girls Football Ltd | Education | 2022 |
| Inspired by Nature Limited | Wholesale & retail | 2020 |
| Insport Consultants Limited | Administrative & support | 1982 |
| Installogix Limited | Construction | 2024 |
| Instant IP Airlinks Limited | Information & communication | 2014 |
| Instant MOT Station Ltd | Wholesale & retail | 2019 |
| Instantyear Property Management Limited | Households | 1991 |
| Integral Change Solutions Limited | Administrative & support | 2022 |
| Integrated Manufacturing Solutions Ltd | Wholesale & retail | 2008 |
| Integrity Defence Solutions UK Limited | Information & communication | 2024 |
| Intelegro Limited | Information & communication | 2022 |
| Intelligent Algorithms Limited | Information & communication | 2017 |
| Intelligent Catering Limited | Professional & scientific | 2010 |
| Intelligent HR Solutions Limited | Professional & scientific | 2014 |
| Inter Used Cars Dealers Ltd | Wholesale & retail | 2024 |
| Interior Gems Ltd | Wholesale & retail | 2022 |
| International Expeditions Limited | Information & communication | 2023 |
| International Military Sales Limited | Public administration | 1990 |
| International Qara Services Ltd | Health & social care | 2016 |
| Interplas Limited | Water & waste | 2020 |
| Interplas Recycling Limited | Water & waste | 2020 |
| Intuition UN Limited | Information & communication | 2004 |
| Investeka Ltd | Real estate | 2019 |
| Involex Holdings Limited | Professional & scientific | 2022 |
| Inwood Bespoke Ltd | Construction | 2025 |
| Ipca Consulting Limited | Professional & scientific | 1990 |
| IPS 2000 Limited | Professional & scientific | 1999 |
| IR Traders Ltd | Construction | 2025 |
| Irinel Transport Ltd | Transport & logistics | 2013 |
| Iris Academies Trust | Education | 2014 |
| Iris Analytical Ltd. | Manufacturing | 2017 |
| Iris Psychotherapy Limited | Health & social care | 2023 |
| IRO Accountants Limited | Professional & scientific | 2011 |
| IRO Pro Accountants Ltd | Professional & scientific | 2025 |
| IRO Properties Limited | Hospitality | 2025 |
| Iron Networks Limited | Information & communication | 2008 |
| Ironside Automotives Ltd | Wholesale & retail | 2024 |
| Ironside Industries Ltd | Wholesale & retail | 2023 |
| Isla-Vee Photography Limited | Professional & scientific | 2018 |
| Islington Kitchens & Interiors Limited | Wholesale & retail | 2019 |
| ISM Pest and Wildlife Services Ltd | Professional & scientific | 2011 |
| Isopower Limited | Professional & scientific | 2013 |
| Issoria Limited | Professional & scientific | 2016 |
| Iszwh Limited | Information & communication | 2015 |
| IT Helpers Limited | Information & communication | 2015 |
| IT Matters Ltd | Professional & scientific | 1997 |
| Italy Direct Ltd | Wholesale & retail | 2013 |
| ITC (Holdings) Limited | Professional & scientific | 1984 |
| ITC Creative Services Limited | Information & communication | 2008 |
| Itesoft UK Limited | Information & communication | 1992 |
| Itrack Systems Limited | Information & communication | 2017 |
| Ivingdon Limited | Households | 1983 |
| Izabella Piskorz Limited | Wholesale & retail | 2025 |
| Izvorski Limited | Real estate | 2017 |
| J Building and Maintenance Ltd | Construction | 2023 |
| J L Welding Ltd | Construction | 2014 |
| J P Decor Limited | Construction | 2007 |
| J P Hale Electrical Services Ltd | Construction | 2020 |
| J Sines Plumbing & Heating Limited | Construction | 2024 |
| J Wong Electrical Limited | Manufacturing | 2021 |
| J&D Energy Solutions Ltd | Professional & scientific | 2011 |
| J&L Fernando Services Limited | Administrative & support | 2019 |
| J-Mac IT Services Ltd | Information & communication | 2024 |
| J. Ranger Ltd | Professional & scientific | 2006 |
| J. S. Brar Ltd | Real estate | 2003 |
| J.G Arts and Crafts Ltd | Wholesale & retail | 2025 |
| J.S. Brar Properties Ltd | Real estate | 2025 |
| J2 & Amor Composite Limited | Manufacturing | 2012 |
| JA Fieldhouse Limited | Information & communication | 2018 |
| Jabbar Holdings Limited | Real estate | 2022 |
| Jacob Phillips Property Services Ltd | Construction | 2020 |
| Jacques Corporation Limited | Wholesale & retail | 2021 |
| Jadebender Arts Ltd | Wholesale & retail | 2014 |
| JAI Guruji Cafe Limited | Hospitality | 2022 |
| JAI Guruji Motors Limited | Wholesale & retail | 2026 |
| JAI Guruji Properties Limited | Real estate | 2024 |
| Jaidev Chana Limited | Wholesale & retail | 2021 |
| Jambec Limited | Real estate | 2016 |
| James Goodman Consulting Ltd | Administrative & support | 2025 |
| James Hogan Marketing Consultant Limited | Professional & scientific | 2021 |
| James Rodger Ltd | Wholesale & retail | 2014 |
| James Scott Golf Ltd | Wholesale & retail | 2024 |
| James Stow Design ETC. Limited | Information & communication | 2022 |
| Jamitc Ltd | Information & communication | 2021 |
| Jan&Co Cleaning Services Ltd | Administrative & support | 2024 |
| JASJAS1 Limited | Hospitality | 2023 |
| Jason Murray Golf Limited | Professional & scientific | 2012 |