| Insightai IT Consultancy Ltd | Information & communication | 2025 |
| Insiteful Retail Property Consultancy Limited | Professional & scientific | 2020 |
| Inspire Tennis Academy Ltd | Education | 2026 |
| Inspired Action Ltd | Other services | 2010 |
| Inspired Concepts Limited | Professional & scientific | 2003 |
| Instant Apostle Ltd | Information & communication | 2011 |
| Intalexretail Ltd | Wholesale & retail | 2025 |
| Intech Consultants Limited | Professional & scientific | 2010 |
| Integrated Environmental Services (IES) Ltd | Professional & scientific | 2011 |
| Integritytech Limited | Information & communication | 2008 |
| Inteka Interiors Ltd | Wholesale & retail | 2015 |
| Intelligent Finishing Systems Limited | Wholesale & retail | 2010 |
| Intelligentq Limited | Wholesale & retail | 2025 |
| Inter Blinds Limited | Manufacturing | 2024 |
| Interkovas Ltd | Transport & logistics | 2019 |
| Internal Refurbishment Group Ltd | Construction | 2019 |
| International Fashion Limited | Wholesale & retail | 2004 |
| International Tennis Coaching Limited | Arts & recreation | 2003 |
| Interstellar Publishing Ltd | Arts & recreation | 2015 |
| Intertwine Services Limited | Health & social care | 2026 |
| Intra Global Solutions Ltd | Real estate | 2017 |
| Intralot Finance UK Limited | Administrative & support | 2007 |
| Intrasales (LYE Lane) Limited | Construction | 1997 |
| Intrix Systems Limited | Information & communication | 2023 |
| Intu-Action Ltd | Professional & scientific | 2021 |
| Intuitive Intelligence Programme Limited | Education | 2007 |
| Investory Limited | Information & communication | 2018 |
| Invictiq Limited | Information & communication | 2014 |
| Ionia Limited | Transport & logistics | 2019 |
| IOT Software Engineering Ltd | Information & communication | 2016 |
| Ipte (UK) Limited | Administrative & support | 1996 |
| Iptogether Limited | Professional & scientific | 2016 |
| Irog Ltd | Real estate | 2023 |
| Iroise Partners UK Limited | Financial services | 2022 |
| Ironwood Advisory Media Consultancy Ltd | Professional & scientific | 2026 |
| Irwin and Colton Limited | Administrative & support | 2016 |
| Ishiika Limited | Wholesale & retail | 2010 |
| Isik Residential Ltd | Real estate | 2025 |
| Isleworth Vapes Ltd | Wholesale & retail | 2018 |
| ISO Building Engineering Ltd | Professional & scientific | 2018 |
| ISO Physio Services Ltd | Health & social care | 2024 |
| ISO Trading Ltd | Financial services | 1999 |
| Issiott Properties Ltd | Real estate | 2021 |
| IT Parts (Europe) Limited | Wholesale & retail | 2014 |
| IT Valley Limited | Information & communication | 2023 |
| Itax(London) Ltd | Real estate | 2023 |
| ITB Project Services Limited | Professional & scientific | 2015 |
| Itss Recruitment Ltd | Administrative & support | 2007 |
| Ivaro Holdings Ltd | Financial services | 2024 |
| Ivaro Ltd | Construction | 2012 |
| Ives Construction Services Limited | Professional & scientific | 2024 |
| Ivfmatters.Com Ltd | Administrative & support | 2011 |
| Ivory Developments Limited | Construction | 2009 |
| Ivory Investments Limited | Professional & scientific | 2009 |
| IW Advisory Limited | Professional & scientific | 2026 |
| IW Operations Limited | Professional & scientific | 2025 |
| J & C Consultants Limited | Professional & scientific | 1998 |
| J & R Lighting Ltd | Construction | 2025 |
| J & V Autos Limited | Administrative & support | 2004 |
| J and C First AID Training Ltd | Education | 2018 |
| J B Self Adhesive Tapes & Labels Limited | Administrative & support | 2001 |
| J Brown Funeral Services Limited | Other services | 2016 |
| J Byne Haulage Limited | Administrative & support | 1999 |
| J C Friend & Sons Glazing Limited | Construction | 2016 |
| J Duffy Plumbing & Heating Limited | Construction | 2014 |
| J F Development Services Limited | Construction | 2016 |
| J G M Management Services Limited | Administrative & support | 2004 |
| J M Coggins Ltd | Professional & scientific | 2025 |
| J M Davies Development and Construction Ltd | Construction | 2025 |
| J M Mcgarvie Limited | Construction | 2015 |
| J S Ventures Limited | Administrative & support | 2007 |
| J Service Ltd | Construction | 2001 |
| J W Ridgeway & Co Limited | Professional & scientific | 2000 |
| J&D TV Limited | Information & communication | 2010 |
| J&N Consultancy Limited | Professional & scientific | 2016 |
| J. Adams Locum Services Ltd. | Professional & scientific | 2013 |
| J. N. York Limited | Professional & scientific | 2015 |
| J. Pikett Associates Limited | Professional & scientific | 2012 |
| J.A. & E.V. Horwood Brothers Limited | Construction | 1959 |
| J.A.R. Surety Management Limited | Financial services | 2023 |
| J.K Doors Ltd | Administrative & support | 2016 |
| J.Skedge and SON Limited | Real estate | 1958 |
| J.T.S. Hill Limited | Wholesale & retail | 2008 |
| JA Technology Services Limited | Information & communication | 2025 |
| Jackaroo Projects Ltd | Construction | 2011 |
| Jackpot Amusements Limited | Arts & recreation | 2003 |
| Jacobs Ladder Music Ltd | Arts & recreation | 2002 |
| Jadeact Limited | Real estate | 2000 |
| JAG Devon Ltd | Real estate | 2024 |
| Jagdish Empire Ltd | Real estate | 2016 |
| Jaidon Limited | Real estate | 2012 |
| Jakester Developments Limited | Construction | 2014 |
| Jalipey Limited | Real estate | 2023 |
| Jamani Investments Limited | Real estate | 2024 |
| James Anthony Enterprises Ltd | Other services | 2013 |
| James Blair & Co Limited | Financial services | 2018 |
| James Peddle Limited | Other services | 1997 |
| James Tomlinson Lighting Limited | Arts & recreation | 2019 |
| James Yard Management Company Limited | Households | 2025 |
| Jamin Sauces Limited | Manufacturing | 2013 |