| Isale Digital Limited | Information & communication | 2021 |
| Isan Holdings Limited | Households | 2026 |
| Isapphire Limited | Administrative & support | 2009 |
| Isarei Global Ltd | Education | 2026 |
| Isfr Medical Ltd | Health & social care | 2021 |
| ISG Holdings Limited | Professional & scientific | 2017 |
| ISH North East Properties Ltd | Real estate | 2019 |
| Ishc Ltd | Arts & recreation | 2024 |
| Ishy Consultancy Ltd | Professional & scientific | 2023 |
| Islamic Essentials Ltd | Wholesale & retail | 2015 |
| Island TAN Limited | Other services | 2025 |
| ISM Civils and Engineering Services Ltd | Construction | 2019 |
| ISM Investment Properties Ltd | Real estate | 2023 |
| ISM Property Ltd | Construction | 2015 |
| ISM Southern Limited | Construction | 2017 |
| ISM Turkish Barber Limited | Other services | 2025 |
| Isobel Porter Social Care Consultancy Services Ltd | Professional & scientific | 2012 |
| Isotherm Insulation Limited | Administrative & support | 2016 |
| Isreb Ltd | Health & social care | 2024 |
| ISS Airview Limited | Transport & logistics | 2024 |
| ISS Facilities Management Limited | Financial services | 2025 |
| Issac Properties Limited | Real estate | 2021 |
| Issm (AS) Ltd | Transport & logistics | 2014 |
| Issueselect Limited | Construction | 1991 |
| Istack Solutions Ltd | Information & communication | 2021 |
| Istanblue Barbering Ltd | Other services | 2021 |
| Istanbul Grill & Pizza Ltd | Hospitality | 2023 |
| IT AU Fait Ltd | Information & communication | 2008 |
| IT Business Partners Limited | Information & communication | 2015 |
| IT Facility Ltd | Information & communication | 2020 |
| IT Networking Ltd | Information & communication | 2011 |
| IT Resource Group Ltd | Information & communication | 2023 |
| IT With Elevate Cloud Ltd | Information & communication | 2025 |
| It's ALL About the Brow Limited | Other services | 2018 |
| Italian Made Eyewear Limited | Wholesale & retail | 2025 |
| Itech Universal Ltd | Wholesale & retail | 2024 |
| Ithaka Productions Limited | Arts & recreation | 2009 |
| Ithink.Dev Ltd | Information & communication | 2023 |
| Itiology Ltd | Construction | 2024 |
| ITL UK Limited | Transport & logistics | 2007 |
| Itp-Global Limited | Extraterritorial | 2024 |
| Itravel NE Ltd | Transport & logistics | 2019 |
| Itrf Engineering Ltd | Construction | 2019 |
| ITS in Black and White Limited | Wholesale & retail | 2023 |
| ITT Commerce Global Limited | Information & communication | 2005 |
| Itty Bitty Underwear Limited | Manufacturing | 2025 |
| IVA Offshore Ltd | Construction | 2013 |
| Ivan Todd Financial Services Ltd | Professional & scientific | 2020 |
| Ivan-Realty Ltd | Real estate | 2024 |
| Ivana Services Ltd | Administrative & support | 2020 |
| Iveson Building Contractors Ltd | Construction | 2018 |
| IVY Farm Court Limited | Professional & scientific | 2004 |
| IVY House Groundworks Limited | Administrative & support | 2013 |
| IVY Property Management Ltd | Households | 2025 |
| IVY Training & Consulting Ltd | Information & communication | 2025 |
| IW Flooring Solutions (NE) Ltd | Construction | 2016 |
| Iweld Solutions Ltd | Manufacturing | 2026 |
| Ixen Technology Limited | Professional & scientific | 2014 |
| Izak 10 Corporation (PVT) Limited | Wholesale & retail | 2022 |
| Izcas Ltd | Education | 2026 |
| Izycky Psychological Services Limited | Professional & scientific | 2012 |
| Izzy Developments Ltd | Financial services | 2007 |
| J & a Property NE Ltd | Real estate | 2019 |
| J & EM Henderson Limited | Financial services | 2018 |
| J & F Williams Limited | Real estate | 2022 |
| J & G Decorators Ltd | Construction | 2022 |
| J & J (Newcastle) Limited | Other services | 2011 |
| J & J International Co-Operation LP | | 2004 |
| J & J Sparkle Deep Cleaning Service Ltd | Administrative & support | 2025 |
| J & J W Garden Limited | Hospitality | 2017 |
| J & L Laurente Limited | Health & social care | 2020 |
| J & M Bluesky Ltd | Wholesale & retail | 2024 |
| J & N Steelcraft NE Ltd | Manufacturing | 2011 |
| J & P Hardware Limited | Wholesale & retail | 1994 |
| J & T LEE Ltd | Wholesale & retail | 2012 |
| J & V Builders Ltd | Construction | 2013 |
| J &G Properties North East Limited | Real estate | 2022 |
| J and W Groundworks Limited | Construction | 2019 |
| J B a Training Design International Limited | Professional & scientific | 2020 |
| J B Drive Ways Ltd | Construction | 2022 |
| J B Ventilation Services Limited | Construction | 2023 |
| J Barbers Gosforth Ltd | Other services | 2019 |
| J Bell Property Investments Limited | Construction | 2015 |
| J C Landscapes (NE) Ltd | Administrative & support | 2022 |
| J C Psychotherapy Limited | Health & social care | 2022 |
| J C Response Limited | Construction | 2010 |
| J Capocci Services Ltd | Wholesale & retail | 2021 |
| J Cardwell Expert Reports Limited | Professional & scientific | 2023 |
| J Coulson Wind Ltd | Energy | 2021 |
| J D Agricultural Limited | Agriculture & fishing | 2018 |
| J D C 2021 Ltd | Professional & scientific | 2021 |
| J DIN Holdings Limited | Real estate | 2025 |
| J G H Property Services Ltd | Administrative & support | 2012 |
| J H a Assets Ltd | Real estate | 2022 |
| J H M Maintenance Limited | Wholesale & retail | 2009 |
| J Investment Group Ltd | Financial services | 2025 |
| J J Piping North East Ltd | Construction | 2024 |
| J Kelly Plant Hire Limited | Administrative & support | 2005 |
| J LAM Investment Ltd | Financial services | 2026 |
| J M a Healthcare Limited | Health & social care | 2005 |