| Hsduk Limited | Professional & scientific | 2024 |
| Hsmii Ltd | Wholesale & retail | 2024 |
| Hssg Inspections Limited | Construction | 2016 |
| HTJ Deakins Limited | Real estate | 2021 |
| Htme Darlington Ltd | Financial services | 2026 |
| HTS Global Ltd | Administrative & support | 2025 |
| Htstg Operating AS School Transport Group Limited | Transport & logistics | 2024 |
| Hubspoke Marketing Ltd | Professional & scientific | 2016 |
| Hudson Catering Limited | Hospitality | 2009 |
| Hudsonn Limited | Wholesale & retail | 2025 |
| Huenmi Limited | Wholesale & retail | 2026 |
| Hughes Bros Construction (Holdings) Limited | Financial services | 2019 |
| Hughes Bros Construction Limited | Construction | 2005 |
| Hughes Bros Farms Ltd | Agriculture & fishing | 2021 |
| Hughes Bros Investments Unlimited | Financial services | 2020 |
| Hughes Bros Plant Hire Limited | Administrative & support | 2019 |
| Hughes Holdings Partnership LLP | | 2025 |
| Hughesg Limited | Wholesale & retail | 2025 |
| Hulls Properties Limited | Real estate | 2024 |
| Hunter Maxwell Associates Limited | Professional & scientific | 2021 |
| Hunters Green Commercials Ltd | Wholesale & retail | 2020 |
| Husband E Limited | Construction | 2019 |
| Hussaria Transport Limited | Transport & logistics | 2014 |
| Hustle Bar Ltd | Hospitality | 2019 |
| Hustle Hive CIC | Education | 2025 |
| Hutchinson Property's Ltd | Hospitality | 2025 |
| Hutchison's Homes Ltd | Real estate | 2026 |
| HW Legal Services Limited | Professional & scientific | 2025 |
| HY Technical Services Ltd | Professional & scientific | 2025 |
| Hyatt Interiors Ltd | Professional & scientific | 2016 |
| Hydraguard Limited | Water & waste | 2000 |
| Hydrofluidics Ltd | Professional & scientific | 2022 |
| Hydrowarm Ltd | Construction | 2020 |
| Hyve Stocks Limited | Wholesale & retail | 2023 |
| I B Renewables Limited | Professional & scientific | 2025 |
| I R Waller Heating & Plumbing Limited | Construction | 2016 |
| I-Evolution Ltd | Professional & scientific | 2006 |
| I. K. a. (U.K.) Limited | Administrative & support | 2002 |
| I. Nails Express Ltd | Wholesale & retail | 2013 |
| I.B.Pharm Consultancy Ltd | Real estate | 2012 |
| I.E Finishings Ltd | Construction | 2019 |
| I2I Financial Planning Group Ltd | Financial services | 2002 |
| I2I Financial Two Ltd | Financial services | 2002 |
| IAN Barras Ltd | Transport & logistics | 2020 |
| IAN Pallas Investments Unlimited | Financial services | 2020 |
| IAN Stabler Transport Limited | Transport & logistics | 2018 |
| IB Trading Group Ltd | Wholesale & retail | 2016 |
| Ibex Bouldering Ltd | Arts & recreation | 2017 |
| Ican Finance Limited | Financial services | 2015 |
| Iconoclast.It Ltd | Information & communication | 2013 |
| IDAN0891 Limited | Other services | 2022 |
| Iddison Dodd and Partners Limited | Construction | 2012 |
| Ideal Breeding Ltd | Agriculture & fishing | 2022 |
| Ideal Upholstery (Darlington) Ltd | Manufacturing | 2017 |
| Idiscountshop Limited | Other services | 2020 |
| IDP Surveying Limited | Professional & scientific | 2012 |
| IDRAGON2023 Limited | Hospitality | 2023 |
| Iexpand Developments Limited | Construction | 2016 |
| Ifix-Property Installations Ltd | Construction | 2015 |
| Igloo Properties North East Ltd | Real estate | 2018 |
| IGO Lettings Ltd | Households | 2022 |
| IGS Properties Ltd | Real estate | 2022 |
| Ihavesignal Limited | Information & communication | 2013 |
| Ijac Industrial Limited | Other services | 2015 |
| IK Performance Ltd. | Wholesale & retail | 2018 |
| Ikhs Property Solutions Ltd | Construction | 2024 |
| IL Picco Ltd | Hospitality | 2023 |
| IL Picco Restaurant Group Limited | Hospitality | 2025 |
| Ildánach Medical Services Limited | Administrative & support | 2022 |
| Illumination Pyrotechnics Limited | Other services | 2021 |
| Image Interior Solutions Ltd | Construction | 2003 |
| Imagine Your Life Limited | Information & communication | 2014 |
| Imagizone Ltd | Arts & recreation | 2021 |
| Imami Cars Ltd | Wholesale & retail | 2024 |
| Imbrand Ltd | Professional & scientific | 2017 |
| Imfg-Nexus UK Ltd | Information & communication | 2025 |
| Immaculate Carpet Ltd | Administrative & support | 2022 |
| IMP Hotel Limited | Real estate | 1977 |
| Imperative Admin Limited | Administrative & support | 2014 |
| Imperial Life Sciences Ltd | Administrative & support | 2020 |
| Imperial Management Services Limited | Administrative & support | 2008 |
| Imperial Spaces Ltd | Real estate | 2026 |
| Impilo Limited | Wholesale & retail | 2016 |
| Impreziv Finishing Limited | Other services | 2005 |
| IN 2 Sport Agency Ltd | Arts & recreation | 2024 |
| IN a Spin Laundry Services Darlington Limited | Other services | 2015 |
| IN Charge Construction Ltd | Construction | 2019 |
| IN Charge Group Ltd | Construction | 2018 |
| IN Charge Properties Ltd | Real estate | 2019 |
| IN House Kitchens Ltd | Wholesale & retail | 2021 |
| IN Over Crest Ltd | Arts & recreation | 2023 |
| IN the Crowd Limited | Extraterritorial | 2026 |
| In-Ex Designs Limited | Wholesale & retail | 2012 |
| In.Formation Studios Ltd | Professional & scientific | 2019 |
| Inchkeith Holdings Limited | Real estate | 2016 |
| Independent Properties NE Ltd | Extraterritorial | 2022 |
| Independent Property & Management Services Limited | Real estate | 1999 |
| Indi Investment Services Ltd | Real estate | 2024 |
| Indian Origins Ltd | Wholesale & retail | 2022 |
| Indigo (NIG) Ltd | Transport & logistics | 2025 |