| I.T Fine Detailing Limited | Other services | 2021 |
| I.T. Software Limited | Information & communication | 2005 |
| Iain Cameron Limited | Construction | 2005 |
| Iain Graham Cattle Services Limited | Administrative & support | 2011 |
| Iain Kyle Limited | Agriculture & fishing | 2002 |
| Iairr Ltd | Transport & logistics | 2025 |
| IAN Armstrong (Carlisle) Limited | Transport & logistics | 1985 |
| IAN Blaylock 24/7 Limited | Transport & logistics | 2013 |
| IAN Dockerty Limited | Construction | 2023 |
| IAN Gibson Associates (Cumbria) Limited | Construction | 2019 |
| IAN Harkness Personal Coaching & Sports Massage Limited | Arts & recreation | 2015 |
| IAN Harrison Fencing & Contracting Limited | Agriculture & fishing | 2008 |
| IAN Johnston Electrical Services Limited | Administrative & support | 2004 |
| IAN Simpson Properties Limited | Real estate | 2016 |
| IBA Engineering Ltd | Professional & scientific | 2021 |
| IC Management Limited | Professional & scientific | 2019 |
| Icarus Programme Services Ltd | Information & communication | 2026 |
| Icon Spa Limited | Other services | 2012 |
| Ideal Living Interiors Limited | Wholesale & retail | 2012 |
| IDG Paterson & SON Limited | Construction | 2008 |
| IFX Carlisle Limited | Real estate | 2010 |
| Ijohnstone Ltd | Transport & logistics | 2026 |
| Ikon Hardware Limited | Real estate | 2009 |
| Ilabel Ltd | Hospitality | 2023 |
| Illuminate Properties Limited | Real estate | 2025 |
| ILR Properties Limited | Real estate | 2014 |
| IM Running Events Ltd | Arts & recreation | 2018 |
| Image Signmakers Limited | Professional & scientific | 2018 |
| Imbibeium Limited | Wholesale & retail | 2024 |
| Imbivium Ltd | Wholesale & retail | 2026 |
| Immortal Art Studio Limited | Arts & recreation | 2011 |
| Immortal Beauty Ltd | Other services | 2015 |
| Immortal Innovations Ltd | Wholesale & retail | 2014 |
| Imon Tandoori Limited | Hospitality | 2019 |
| Impact Coaching Worldwide Ltd | Professional & scientific | 2016 |
| Impactsett Limited | Real estate | 1982 |
| Imperium Life Ltd | Information & communication | 2025 |
| Impi Projects Limited | Construction | 2018 |
| IN & OUT Mini Market Limited | Wholesale & retail | 2025 |
| In-Decor (UK) Limited | Construction | 2006 |
| Inandout Local Ltd | Wholesale & retail | 2026 |
| Independent Adventure Limited | Administrative & support | 2016 |
| Independent Park Network Ltd | Hospitality | 2020 |
| Indian Tiffin House Limited | Hospitality | 2024 |
| Indie D Tattoo Ltd | Other services | 2020 |
| Indulge at NO.15 Limited | Hospitality | 2025 |
| Infinity Print Solutions Ltd | Information & communication | 2002 |
| Ingleton Driving Ltd | Transport & logistics | 2023 |
| INK 58 Limited | Other services | 2013 |
| Innoapps Ltd | Information & communication | 2017 |
| Innovate Leads Ltd | Professional & scientific | 2023 |
| Innovation Sports (Cumbria) Ltd | Arts & recreation | 2018 |
| Inox Design Limited | Manufacturing | 2006 |
| Inputloop Limited | Administrative & support | 2002 |
| Insight Rehabilitation Specialists Limited | Health & social care | 2012 |
| Inspektris Limited | Extraterritorial | 2019 |
| Insumate Limited | Administrative & support | 2008 |
| Insure Direct Limited | Administrative & support | 1967 |
| Intech Services (Cumbria) Ltd | Information & communication | 2017 |
| Integra Toshika Properties Ltd | Real estate | 2026 |
| Integrity Office Limited | Information & communication | 2008 |
| Intek Ceilings Limited | Construction | 2008 |
| Intek Shopfitting Solutions Limited | Construction | 2010 |
| Interfire Ltd | Wholesale & retail | 2008 |
| Interfresh Produce Ltd | Hospitality | 2020 |
| Intricate Property Ltd | Real estate | 2022 |
| Intricate Training Ltd | Education | 2021 |
| Intro PR and Social Media Ltd | Administrative & support | 2017 |
| Investacc Holdings Limited | Financial services | 2010 |
| Investacc Limited | Financial services | 1992 |
| Investacc Pension Administration Limited | Financial services | 2010 |
| Investacc Pension Trustees Limited | Financial services | 1993 |
| Investacc Properties Limited | Real estate | 2016 |
| Investacc Wealth Management Limited | Extraterritorial | 2020 |
| Investment Trustee and Adviser Ltd | Financial services | 2014 |
| Invisolar Ltd | Extraterritorial | 2021 |
| ION Lettings Limited | Real estate | 2024 |
| IP River Networks Ltd | Information & communication | 2017 |
| Ipson Ltd | Hospitality | 2022 |
| Iridium Supplies Limited | Wholesale & retail | 2018 |
| Iris Fashion Limited | Wholesale & retail | 2020 |
| Iron Peak Delivery Ltd | Transport & logistics | 2026 |
| Iron Peak Ltd | Transport & logistics | 2025 |
| Iropinca Ltd | Transport & logistics | 2025 |
| Irthing Developments Limited | Construction | 2016 |
| Irthing Electrical Limited | Construction | 2021 |
| Irthing Vale Quality Foods Limited | Wholesale & retail | 2002 |
| Irvine House Limited | Hospitality | 2016 |
| Irvine Refrigeration Limited | Manufacturing | 2014 |
| Irving Builders Limited | Construction | 2006 |
| Irving of Dalston Limited | Transport & logistics | 2025 |
| Irving's Taxi Hire Ltd | Transport & logistics | 2023 |
| ISI Healthcare Limited | Transport & logistics | 2022 |
| ISI Tech Limited | Information & communication | 2026 |
| Isle International Transport Ltd | Transport & logistics | 2022 |
| Isle Studio (Carlisle) Ltd | Professional & scientific | 2025 |
| Islington Centre for English Limited | Education | 2007 |
| IT Takes a Village Nursery and Pre-School Ltd | Health & social care | 2025 |
| It's Clean Limited | Administrative & support | 2007 |
| It.Is.We Limited | Hospitality | 2016 |