| Interface International Limited | Wholesale & retail | 2005 |
| Interfaro Limited | Professional & scientific | 2022 |
| Interfix Car Garage UK Ltd | Wholesale & retail | 2019 |
| Interiors of Aylesbury Ltd | Administrative & support | 2010 |
| Interligo Limited | Professional & scientific | 2024 |
| Interlink Electrical Services Ltd | Construction | 2023 |
| Interlink Properties Limited | Real estate | 2024 |
| International Association for Relational Transactional Analysis | Education | 2009 |
| International Cars Ltd | Wholesale & retail | 2015 |
| International Funerals Ltd | Other services | 2018 |
| International Therapeutic Initiative Ltd. | Health & social care | 1986 |
| Interserve Enterprise Ltd | Transport & logistics | 2023 |
| Intex Building and Property Services Ltd | Construction | 2019 |
| Introversa Limited | Professional & scientific | 2014 |
| Intuitiv Digital Ltd | Information & communication | 2025 |
| Intupeak Limited | Professional & scientific | 2025 |
| Intyric Ltd | Professional & scientific | 2026 |
| INU Cart Ltd | Wholesale & retail | 2026 |
| Invalifts Limited | Construction | 2000 |
| Invanity Marketing Ltd | Professional & scientific | 2019 |
| Invicos (AYL) Limited | Construction | 2024 |
| Invicta Distribution Ltd | Wholesale & retail | 2020 |
| Invictus Air Conditioning Limited | Construction | 2025 |
| Invisifirm Ltd | Wholesale & retail | 2023 |
| Invision Ltd | Arts & recreation | 2026 |
| ION Marketing Ltd | Professional & scientific | 2019 |
| Ion's Angels Limited | Manufacturing | 2025 |
| Ionego Trans Ltd | Transport & logistics | 2014 |
| Ionut Roinita Limited | Transport & logistics | 2017 |
| Iota IT Services Ltd | Information & communication | 2023 |
| IP & I Enterprises Limited | Professional & scientific | 2008 |
| Ipro Football Coaching Limited | Education | 2018 |
| Ipro Holdings Limited | Professional & scientific | 2021 |
| Ipro Manufacturing Limited | Manufacturing | 2001 |
| Iqbal Traders Limited | Hospitality | 2025 |
| Irish German Transport Limited | Transport & logistics | 2016 |
| Iroegbu Homes Ltd | Real estate | 2022 |
| Iron Security (UK) Ltd | Administrative & support | 2009 |
| Irreal Ltd | Information & communication | 2014 |
| Irsa Properties Limited | Real estate | 2021 |
| Irsa Solutions Limited | Information & communication | 2011 |
| Irving International Talent Ltd | Administrative & support | 2024 |
| IS Analytics Ltd | Information & communication | 2018 |
| ISA Building Ltd | Construction | 2015 |
| Isabel Grua Life Harmony Styling Ltd. | Information & communication | 2017 |
| Isabelle MAG Limited | Health & social care | 2014 |
| Isambard and Joe's Family Pubs Ltd | Hospitality | 2011 |
| ISC Transport Ltd | Transport & logistics | 2026 |
| Ishanth Consultancy Services Limited | Information & communication | 2019 |
| Ishi Limited | Information & communication | 2025 |
| Ishi Yuvi Property Ltd | Real estate | 2021 |
| Ishyash Ltd | Real estate | 2023 |
| Isis Concepts Holdings Limited | Financial services | 2012 |
| Isma'El Halal Meats Limited | Manufacturing | 2015 |
| ISO Cars Ltd | Administrative & support | 2025 |
| Isotopic Studios Ltd | Information & communication | 2025 |
| Istanbul Kebab Aylesbury Ltd | Hospitality | 2023 |
| Istanbul Wendover Ltd | Hospitality | 2019 |
| Iswadesi Private Limited | Wholesale & retail | 2020 |
| IT Empathy Limited | Information & communication | 2016 |
| IT IS NOT Your Ltd | Wholesale & retail | 2022 |
| IT Mission Consulting Ltd | Information & communication | 2026 |
| IT Remedies Limited | Information & communication | 2009 |
| IT System Integrators Ltd | Information & communication | 2014 |
| It's S.O. ALL About YOU Ltd | Other services | 2022 |
| Iterium Ltd | Administrative & support | 2016 |
| Ithika Ltd | Professional & scientific | 2018 |
| Itops Solutions Ltd | Information & communication | 2020 |
| IVA Trans Ltd | Transport & logistics | 2018 |
| Ivaris Limited | Wholesale & retail | 2008 |
| Ivor Miles Limited | Wholesale & retail | 1995 |
| J & D Heating Services Ltd | Construction | 2025 |
| J & E Prime Builders Ltd | Construction | 2026 |
| J & J Farms Limited | Agriculture & fishing | 2017 |
| J & N Transport AYL Limited | Wholesale & retail | 2025 |
| J & S Aftercare II Ltd | Administrative & support | 2024 |
| J & S R (Lyme) Ltd. | Real estate | 2013 |
| J & S Scapes Limited | Construction | 2005 |
| J & T Hooker Investments Limited | Construction | 2011 |
| J B B Carpentry Ltd | Construction | 2015 |
| J B Capital Group Limited | Financial services | 2021 |
| J B K Partnership Limited | Wholesale & retail | 2005 |
| J B Systems Limited | Manufacturing | 2005 |
| J C & S Holdings Ltd | Financial services | 2019 |
| J C King Limited | Professional & scientific | 2003 |
| J E Barnes Transport Ltd | Transport & logistics | 2026 |
| J F Agricultural Limited | Wholesale & retail | 2019 |
| J H Stockwell Limited | Manufacturing | 2011 |
| J Home Lettings Ltd | Real estate | 2023 |
| J J Matthews Limited | Financial services | 2015 |
| J J Richardson Limited | Professional & scientific | 2020 |
| J M Grounds Maintenance Ltd | Administrative & support | 2025 |
| J Maxx Salon Limited | Other services | 2023 |
| J P & M Holdings Limited | Professional & scientific | 2011 |
| J R Davies Associates Limited | Other services | 2001 |
| J S Builders (Aylesbury) Ltd | Construction | 2017 |
| J Sayell Plastering & General Building Ltd | Construction | 2024 |
| J Shakespeare Hygienist Ltd | Health & social care | 2015 |
| J Thomson Roofing Ltd | Construction | 2026 |
| J Woodley Fitness Ltd | Arts & recreation | 2024 |