| HW 1234 Limited | Professional & scientific | 2013 |
| HW Heating Limited | Construction | 2019 |
| HW Services (Southern) Ltd | Other services | 2026 |
| HWG Services Limited | Construction | 1996 |
| HX2 Consultancy Limited | Administrative & support | 2016 |
| Hyde Specsavers Hearcare Limited | Wholesale & retail | 2019 |
| Hyde Specsavers Limited | Wholesale & retail | 1992 |
| Hyde Visionplus Limited | Wholesale & retail | 1992 |
| Hydraflyte Limited | Professional & scientific | 2020 |
| HYE Oak Limited | Wholesale & retail | 1997 |
| Hyland Homes Southern Limited | Construction | 2025 |
| Hypersonic Ltd | Information & communication | 2026 |
| Hypnotherapy and Coaching Solutions Ltd | Education | 2026 |
| Hypnotherapy Blend Solution Ltd | Health & social care | 2024 |
| Hyssop TEN Limited | Wholesale & retail | 2018 |
| Hythe Specsavers Limited | Wholesale & retail | 2023 |
| I D Mcintyre Limited | Real estate | 2023 |
| I Love to Learn Fareham LLP | | 2024 |
| I Macaskill Ltd | Information & communication | 2025 |
| I&S Interior Systems Limited | Administrative & support | 2011 |
| I.Am.S.Brown Limited | Professional & scientific | 2021 |
| I.C. Endocrine Services Ltd. | Health & social care | 2012 |
| I.C.B.T. Company Limited | Professional & scientific | 1985 |
| I.M.D. (UK) Limited | Wholesale & retail | 1998 |
| I.T.P.M. (London and South East) Limited | Other services | 2008 |
| Iaim Investments Limited | Real estate | 2026 |
| IAN Birkett Plant Services Limited | Construction | 1997 |
| IAN Bull Limited | Administrative & support | 2002 |
| IAN Gray Builders Ltd | Construction | 2013 |
| IAN Waterfall Consultancy Ltd | Professional & scientific | 2022 |
| IAN Whyte Solutions Ltd | Professional & scientific | 2018 |
| IAS Services Limited | Construction | 2019 |
| IBC Rental Limited | Administrative & support | 2017 |
| Iblen Signal Engineering Ltd | Education | 2015 |
| Ibrustar Limited | Real estate | 2019 |
| IC Composites Limited | Professional & scientific | 2021 |
| IC Consultancy 247 Ltd | Professional & scientific | 2025 |
| Icareimove Limited | Health & social care | 2017 |
| Icbt (Medical) Company Limited | Wholesale & retail | 1989 |
| Ice Cubed 1 LLP | | 2017 |
| ICH Wight Decking Limited | Construction | 2021 |
| Icon Media Solutions Ltd | Information & communication | 2014 |
| ID Image Consultancy Ltd | Other services | 2009 |
| Ideal Property Services Limited | Real estate | 2016 |
| Ideal Window Solutions Limited | Construction | 1998 |
| Idio Web Services Ltd | Information & communication | 2019 |
| Idle Specsavers Limited | Wholesale & retail | 1987 |
| Idle Visionplus Limited | Wholesale & retail | 1993 |
| IDS Solutions Limited | Information & communication | 2010 |
| Ieska Sport Centre Ltd | Arts & recreation | 2017 |
| IFA Compliance Solutions Limited | Financial services | 2009 |
| Ifast Diagnostics Limited | Manufacturing | 2022 |
| Ignite Consult Ltd | Information & communication | 2020 |
| IGS Motorsport Limited | Wholesale & retail | 2026 |
| Ihome Property Service LLP | | 2025 |
| IJC Construction Consultants Limited | Professional & scientific | 2024 |
| Ikiru Advisory Limited | Professional & scientific | 2025 |
| IL Manicomio Limited | Hospitality | 2019 |
| Ilford Specsavers Limited | Wholesale & retail | 1993 |
| Ilford Visionplus Limited | Wholesale & retail | 1993 |
| Iliac Design Limited | Wholesale & retail | 1998 |
| Ilimit Logistic Ltd | Transport & logistics | 2017 |
| Ilkeston Specsavers Hearcare Limited | Wholesale & retail | 2013 |
| Ilkley Specsavers Limited | Wholesale & retail | 2008 |
| Ilkley Visionplus Limited | Wholesale & retail | 2008 |
| Illumr Limited | Information & communication | 2008 |
| ILS Management Consultants Limited | Professional & scientific | 2013 |
| Image Creative Group Limited | Financial services | 2018 |
| Image Creative Partnership Limited | Professional & scientific | 2005 |
| Image Windows (UK) Limited | Construction | 2008 |
| Imaging Components Ltd | Information & communication | 2024 |
| Imaji Nation Limited | Hospitality | 2025 |
| Imajine Holdings Limited | Real estate | 2024 |
| IMG Tech Ltd | Manufacturing | 2025 |
| IMI Europe Limited | Administrative & support | 1999 |
| Immaculate Valeting Limited | Wholesale & retail | 2015 |
| Impact Care-Uk Limited | Health & social care | 2021 |
| Impactready Limited | Professional & scientific | 2013 |
| Imperial Boerboels Ltd | Agriculture & fishing | 2025 |
| Imperial Homes Limited | Construction | 1987 |
| Imperium Grading Ltd | Administrative & support | 2025 |
| Imperium Property Consultants Limited Liability Partnership | | 2024 |
| IMS Technology Services Limited | Information & communication | 2001 |
| IN Deep Technology Limited | Manufacturing | 2007 |
| IN Situ Media Limited | Extraterritorial | 2003 |
| IN Situ Sports & Leisure Advertising Limited | Extraterritorial | 2003 |
| IN10SITY Ltd | Professional & scientific | 2018 |
| IN2 Flooring Ltd | Wholesale & retail | 2024 |
| IN2 Systems Limited | Professional & scientific | 2017 |
| Incendo Development Ltd | Professional & scientific | 2013 |
| Incognito Special Effects Ltd | Information & communication | 2015 |
| Incomm Digital Solutions International Limited | Administrative & support | 2012 |
| Incomm Europe Limited | Information & communication | 2004 |
| Incus Communications Holding Limited | Financial services | 2025 |
| Incus Communications Ltd | Professional & scientific | 2025 |
| Independent Attachment Services London Ltd | Health & social care | 2020 |
| Independent Project Consultant Limited | Professional & scientific | 2012 |
| Index Industries Ltd | Manufacturing | 2023 |
| Indigo Accounts Ltd | Professional & scientific | 2014 |
| Indigo App Solutions Ltd | Financial services | 2026 |