| Ilpond Limited | Professional & scientific | 2007 |
| IM Engineering UK Limited | Water & waste | 2006 |
| Imad Sheikh Limited | Wholesale & retail | 2022 |
| Iman Technology Limited | Information & communication | 1997 |
| Impossible Object Ltd | Professional & scientific | 2019 |
| Imrose Properties Limited | Real estate | 1985 |
| Inbox Solutions Limited | Manufacturing | 1999 |
| Inchgower GEO Limited | Mining & quarrying | 2025 |
| Incorporated Phonographic Society,(The) | Other services | 1898 |
| Independent Computer Engineering Limited | | 1977 |
| Independent Systems Solutions Limited | Information & communication | 1996 |
| Indexquick Limited | Professional & scientific | 1978 |
| Indian Homefood and Beverages Limited | Hospitality | 2004 |
| Indiana Advice Ltd | Financial services | 2024 |
| Indoor Garden Investment Co.Limited | Financial services | 1962 |
| Industra Services Ltd | Other services | 2004 |
| Infinity Star Investment Limited | Real estate | 2024 |
| Inforange Limited | Professional & scientific | 1985 |
| Ingersoll Locks Limited | Professional & scientific | 2015 |
| Ingle Close Management Limited | Households | 1989 |
| Innotel Consulting Limited | Real estate | 2003 |
| Innovata Business Solutions Limited | Professional & scientific | 2006 |
| Innovative Operators Ltd | Administrative & support | 2021 |
| Inoso Limited | Wholesale & retail | 2006 |
| Inservio Limited | Information & communication | 2002 |
| Inspire Promotions Ltd | Wholesale & retail | 1996 |
| Instant Creations Limited | Professional & scientific | 2007 |
| Insureiq Ltd | Financial services | 2024 |
| Inta-Net Limited | Professional & scientific | 1996 |
| Integration Engineering Limited | Professional & scientific | 2006 |
| Intel Marketing Ltd | Administrative & support | 2009 |
| Intellego Group Limited | Professional & scientific | 2002 |
| Intelligent Music Enterprises Limited | Arts & recreation | 2005 |
| Intellisource Ltd | Information & communication | 2002 |
| Intellitech I.T. Solutions Limited | Information & communication | 2006 |
| Inteo Limited | Construction | 2005 |
| Interchange Consulting Limited | Professional & scientific | 2008 |
| Interface Components Limited | Wholesale & retail | 2002 |
| Interiors Construction Ltd | Construction | 2013 |
| International Investment Associates Limited | Financial services | 2024 |
| International Lifestyle Ltd | Arts & recreation | 2013 |
| International Trade Promotions Limited | Information & communication | 2012 |
| Internet Rewards Ltd | Information & communication | 2005 |
| Interstruction Limited | | 1974 |
| Interworld Computers Limited | Information & communication | 1986 |
| Intreck Limited | Information & communication | 2004 |
| INTRO2ENTERPRISE Limited | Professional & scientific | 2009 |
| Inventionnaire Limited | Wholesale & retail | 2015 |
| Investable Limited | Professional & scientific | 1971 |
| Investment Funding Advisers Limited | Professional & scientific | 1991 |
| Invicta Film Nominees Limited | Administrative & support | 2001 |
| Invision Media Limited | Information & communication | 2007 |
| Ionel Services Limited | Construction | 2016 |
| IOT Studio Ltd. | Information & communication | 2017 |
| Iqbal & Sons Enterprises Limited | Wholesale & retail | 2025 |
| Iqdos Limited | Professional & scientific | 2004 |
| Irving Homes Limited | Real estate | 2005 |
| Irwin Consultancy Services Ltd. | Administrative & support | 2007 |
| Isca Investments Limited | Real estate | 1991 |
| Ishana Limited | Real estate | 2010 |
| Isis DC Limited | Other services | 2006 |
| Island Graphics Design Consultancy Limited | Arts & recreation | 1996 |
| Islet Group Limited | Information & communication | 2000 |
| Issie B Limited | Professional & scientific | 2004 |
| Issp Limited | Information & communication | 2004 |
| IT Computer Systems Limited | Information & communication | 1999 |
| It's a Honour Roofing Ltd | Construction | 2026 |
| Itana Beauty Limited | Other services | 2025 |
| Itanta Ltd | Information & communication | 2007 |
| Itbiz Limited | Wholesale & retail | 2013 |
| Ithaka Consulting Limited | Health & social care | 2002 |
| Itil Consultancy Limited | Professional & scientific | 2007 |
| Iufp Global Limited | Education | 2018 |
| IV Drip Clinic Ltd | Health & social care | 2022 |
| IVO Prints Limited | Extraterritorial | 2007 |
| Ivorybond Limited | Wholesale & retail | 1983 |
| IVY Leaf Music Limited | Arts & recreation | 2000 |
| IZK Ltd | Real estate | 2018 |
| J & a Motors Limited | Wholesale & retail | 2000 |
| J & C Sawblades Limited | | 1988 |
| J & C Wisdom Properties Limited | Real estate | 2016 |
| J & H Enterprises Limited | Wholesale & retail | 2017 |
| J & J Security Maintenance Limited | Administrative & support | 2012 |
| J & JAY Properties Limited | Construction | 2007 |
| J & M Launderettes (Staines) Limited | Other services | 1978 |
| J & R Giles Mechanical Services Limited | | 1976 |
| J B Building Contractors Ltd | Construction | 2004 |
| J Coffey Plant Limited | Construction | 2004 |
| J Freight Logistics Limited | Transport & logistics | 2006 |
| J Gill Properties Ltd | Real estate | 2020 |
| J J C Transport Limited | Transport & logistics | 1998 |
| J J Food &Wine (NW10) Limited | Wholesale & retail | 2021 |
| J J Global Limited | Professional & scientific | 2002 |
| J M Cockerton Services Limited | Professional & scientific | 2006 |
| J P Mann Consulting Limited | Professional & scientific | 2008 |
| J&J London Limited | Professional & scientific | 2012 |
| J. and Y. Investments Limited | Wholesale & retail | 1978 |
| J. Coffey Construction Limited | Construction | 1994 |
| J. Davies (Agents) Limited | Real estate | 1958 |
| J. Davies Charities Limited | Health & social care | 1966 |