| Identify Action Marketing Consultancy Limited | Professional & scientific | 2020 |
| Idris Operations Limited | Professional & scientific | 2024 |
| IDV Logistics Ltd | Transport & logistics | 2024 |
| Iexpand Developments (Silverstone a) Limited | Real estate | 2017 |
| Ifocs Ltd | Real estate | 2024 |
| Ifrim Marius Ltd | Transport & logistics | 2016 |
| IFS Business Support Services LLP | | 2008 |
| Igloo Planning Services Limited | Professional & scientific | 2017 |
| IJC Accounting & Taxation Services Limited | Professional & scientific | 2010 |
| IJZ Enterprises Ltd | Wholesale & retail | 2026 |
| Illuma Health Communications Limited | Professional & scientific | 2017 |
| Image Asset Management Limited | Professional & scientific | 2006 |
| Image Content Collections Limited | Wholesale & retail | 2008 |
| Imed Consultancy Limited | Professional & scientific | 2012 |
| Imed Holdings Limited | Financial services | 2023 |
| Imela Care Limited | Health & social care | 2017 |
| Impact Evaluation Services Limited | Professional & scientific | 1979 |
| Impact FD Limited | Professional & scientific | 2020 |
| IN 2 Components Limited | Extraterritorial | 1999 |
| IN Working Order Limited | Real estate | 1995 |
| Inapub Limited | Other services | 2010 |
| Inboundology Limited | Administrative & support | 2012 |
| Independent Financial Strategies (Horley) LLP | | 2007 |
| Independent Food Republic Ltd | Manufacturing | 2025 |
| Indian Pantry Ltd | Real estate | 2011 |
| Indigenous House Limited | Manufacturing | 2019 |
| Indigo Reverso Limited | Information & communication | 2025 |
| Individual Creations Ltd | Wholesale & retail | 2020 |
| Indulgence Candles Ltd | Professional & scientific | 2014 |
| Indulging Limited | Hospitality | 2006 |
| Industrial Fire Protection Association of Great Britain Limited(The) | Professional & scientific | 1965 |
| Industrial Lightworks Ltd | Information & communication | 2026 |
| Industrial Mathematical Modelling Ltd | Professional & scientific | 2023 |
| Infectedmonkzcoventry Ltd | Arts & recreation | 2025 |
| Infectedmonkztattoo Studio Ltd | Education | 2023 |
| Infinite Selections Ltd | Wholesale & retail | 2023 |
| INGENIOUS8 Limited | Professional & scientific | 2020 |
| Ingrid Raphael Limited | Other services | 2021 |
| Ings-Uk Ltd | Wholesale & retail | 2025 |
| INK and Acre Procurement Ltd | Professional & scientific | 2026 |
| Inkit Services Ltd | Wholesale & retail | 2016 |
| INNOV8 Samples and Merchandising Limited | Administrative & support | 2012 |
| Innova Mechanics Limited | Professional & scientific | 2024 |
| Insight Bookkeeping & Accounting Services Limited | Administrative & support | 2000 |
| Insight Creation Limited | Professional & scientific | 2012 |
| Insight Warehouse Limited | Professional & scientific | 2010 |
| Insightability Ltd | Professional & scientific | 2021 |
| Insightful Retreats Limited | Education | 2024 |
| Inspire Law Limited | Professional & scientific | 2007 |
| Inspirum.Uk Ltd | Wholesale & retail | 2025 |
| Integra 8 Limited | Professional & scientific | 2000 |
| Integration Technology Limited | Extraterritorial | 2001 |
| Intelliapps Limited | Information & communication | 2010 |
| Intelligent Assistance Ltd | Information & communication | 2026 |
| Intelligent Assistant Ltd | Information & communication | 2025 |
| Intercept Accounting Limited | Professional & scientific | 2024 |
| Interstellar AI Ltd | Information & communication | 2024 |
| Intouch Brands Limited | Financial services | 2021 |
| Investorcom Limited | Information & communication | 2000 |
| Invia Consulting Ltd | Information & communication | 2014 |
| Invo Metal Ltd | Manufacturing | 2023 |
| Involvement Employee Ownership Trustee Limited | Professional & scientific | 2025 |
| Involvement Limited | Wholesale & retail | 1981 |
| Involvement Packaging Limited | Extraterritorial | 2022 |
| Invopak Limited | Extraterritorial | 2006 |
| Ioctl Ltd | Manufacturing | 2019 |
| Ionut Dorel Limited | Transport & logistics | 2025 |
| Iopener Holdings Limited | Other services | 2007 |
| Iopener Limited | Education | 2003 |
| Iphixx Limited | Other services | 2013 |
| Iphone-Experts Ltd | Wholesale & retail | 2013 |
| IPL Capital Limited | Extraterritorial | 2000 |
| Iqbal ALI LLP | | 2005 |
| IRA & Isla Baby and Kids Ltd. | Wholesale & retail | 2013 |
| Iridium Motors Ltd | Wholesale & retail | 2021 |
| IRL Engineering Ltd | Professional & scientific | 2019 |
| IRM Carpentry & Building Limited | Manufacturing | 2012 |
| Iron and Wood (Kidlington) Ltd | Wholesale & retail | 2016 |
| Iron and Wood Fitting Services Ltd | Construction | 2013 |
| Iron and Wood Ltd | Wholesale & retail | 2008 |
| Iron Down Hill Limited | Real estate | 2021 |
| Ironclad Productions Limited | Information & communication | 2001 |
| ISC Steelwork Ltd | Manufacturing | 2024 |
| Iserin Medical Ltd | Health & social care | 2013 |
| ISJ Construction Ltd | Construction | 2019 |
| ISJ Engineering Limited | Professional & scientific | 2014 |
| Isjb Holdings Limited | Financial services | 2022 |
| Isjb Property Limited | Real estate | 2022 |
| Ismatix Cleaning Solutions Ltd. | Administrative & support | 2024 |
| ISO Certification Support Ltd | Professional & scientific | 2018 |
| Isquared Insight & Innovation Limited | Professional & scientific | 2009 |
| IST Intech Limited | Professional & scientific | 1998 |
| Istanbul Barber Banbury Ltd | Other services | 2018 |
| IT Communication Solutions Limited | Other services | 2003 |
| IT Wizard Group Limited | Other services | 2016 |
| It's a Chocolate Thing Limited | Manufacturing | 2016 |
| It's ALL About M.E. Banbury Limited | Other services | 2012 |
| ITD Building Services Limited | Construction | 2023 |
| Ithaca Environmental Ventures Limited | Information & communication | 2009 |
| Itsinc Ltd | Agriculture & fishing | 2018 |