| INB Flooring Ltd | Construction | 2026 |
| Inbrico Limited | Construction | 2018 |
| Inca Builders Ltd | Construction | 2025 |
| Inceptum Risk Management Ltd | Administrative & support | 2022 |
| Inch Recyling Solutions Ltd | Water & waste | 2017 |
| Inch Retail Stock Ltd | Wholesale & retail | 2020 |
| Inchworth Limited | Real estate | 1997 |
| Includiverse Limited | Information & communication | 2025 |
| Inclusivity Holdings Ltd | Financial services | 2023 |
| Incolo Limited | Real estate | 2016 |
| Indalo International Holdings Limited | Professional & scientific | 2015 |
| Independent Fitness Training Ltd | Arts & recreation | 2023 |
| Independent Hotel Management Ltd | Hospitality | 2022 |
| Independent Power Technologies Limited | Professional & scientific | 2013 |
| Independent Windows South West Ltd | Construction | 2014 |
| Indian EYE (Plymouth) Ltd | Hospitality | 2014 |
| Indian Fresh Fish and Meat Ltd | Hospitality | 2024 |
| Indian Rose Ltd | Hospitality | 2021 |
| Indiana Health Care Services Limited | Health & social care | 2015 |
| Indochina Starfish Foundation | Education | 2006 |
| Indus Devon Curry House Ltd | Hospitality | 2025 |
| Indus Fashion Ltd | Wholesale & retail | 2022 |
| Industrial Component Supplies Limited | Wholesale & retail | 2002 |
| Infinite Fire Systems Ltd | Construction | 2026 |
| Infinite Services SW Ltd. | Construction | 2010 |
| Infinite Surface Repairs Ltd | Other services | 2015 |
| Infinite Systems SW Ltd | Extraterritorial | 2016 |
| Infinite Tiling Ltd | Construction | 2017 |
| Infinity Keepsakes Ltd | Wholesale & retail | 2024 |
| Inflatex Limited | Wholesale & retail | 2013 |
| Influential Plus Limited | Information & communication | 2025 |
| Ingleside Plymouth Management Company Limited | Households | 2008 |
| Ingoldby Rhodes Ltd | Professional & scientific | 2017 |
| Inhouse Golf Limited | Administrative & support | 2026 |
| Inis Interiors Ltd | Professional & scientific | 2025 |
| Initiol Limited | Professional & scientific | 2002 |
| Inked Tattoo Studio Ltd | Arts & recreation | 2013 |
| Inkey Works Ltd | Professional & scientific | 2026 |
| Inner Calm Kitley CIC | Real estate | 2020 |
| Inner Circle Ltd. | Professional & scientific | 2019 |
| Innovation Boost Ltd | Professional & scientific | 2025 |
| Innovtech Ltd | Professional & scientific | 2025 |
| Inntelligence Ltd | Hospitality | 2007 |
| Inplace Health Ltd | Health & social care | 2023 |
| Inside Housing Solutions Limited | Administrative & support | 2006 |
| Insight Energy Systems Ltd | Construction | 2016 |
| Insight Property Claims Ltd | Other services | 2023 |
| Insight Study Limited | Education | 2009 |
| Insite Solutions Limited | Information & communication | 2003 |
| Inskill Consultancy Limited | Professional & scientific | 2008 |
| Insp (UK) Ltd | Health & social care | 2024 |
| Inspi Ltd | Wholesale & retail | 2025 |
| Inspiraology Ltd | Education | 2018 |
| Inspiration HUT Ltd | Professional & scientific | 2017 |
| Inspire Construction SW Ltd | Construction | 2018 |
| Inspire Spirit Ltd | Information & communication | 2018 |
| Inspire Wealth Holdings Ltd | Financial services | 2020 |
| Inspire Wealth Ltd | Financial services | 2006 |
| Inspired Creative Design 2011 Ltd | Manufacturing | 2012 |
| Install Recycling Limited | Water & waste | 2024 |
| Instant Justice Limited | Administrative & support | 2021 |
| Instantbase Limited | Construction | 1987 |
| INT64 Software Limited | Information & communication | 2014 |
| Intact Management Ltd | Wholesale & retail | 2013 |
| Intact Stores Ltd | Wholesale & retail | 2019 |
| Integral Partitioning and Ceilings Limited | Construction | 2017 |
| Integrated Ventures Ltd | Health & social care | 2024 |
| Intellec Ltd. | Extraterritorial | 2011 |
| Intelligent Conscious Research Innovations (Icri) Ltd | Health & social care | 2016 |
| Intelligent Design Solutions in Architecture Ltd | Professional & scientific | 2016 |
| Intelligent Optimisations Limited | Professional & scientific | 2016 |
| Intense ABC CIC | Arts & recreation | 2025 |
| Intentium Limited | Extraterritorial | 1999 |
| Interactive Commerce Ltd | Information & communication | 2015 |
| Intercity Studio Ltd | Professional & scientific | 2015 |
| Interdirect Magazines Ltd | Professional & scientific | 2020 |
| Interfish Producer Organisation Limited | Agriculture & fishing | 2008 |
| Interfit Installations Limited | Construction | 2009 |
| Intergo Holdings Limited | Financial services | 2020 |
| Interlock Brickwork Ltd | Construction | 2019 |
| Intermedia Brand Marketing Limited | Administrative & support | 2010 |
| International Foods Group Limited | Wholesale & retail | 2024 |
| International Marine Recruitment Ltd | Administrative & support | 2026 |
| Interseal (SW) Limited | Construction | 2008 |
| Intersend Limited | Transport & logistics | 2012 |
| Intra-Laboratories Ltd | Wholesale & retail | 2017 |
| Intuitable Ltd. | Professional & scientific | 2015 |
| Investment-E Ltd | Transport & logistics | 2019 |
| IO Exchange Limited | Information & communication | 2025 |
| ION Properties Ltd | Real estate | 2021 |
| Iorn Group UK Limited | Wholesale & retail | 2023 |
| Iota Care Limited | Health & social care | 2011 |
| Ioutlet Holdings Ltd | Financial services | 2018 |
| Ioutlet Limited | Financial services | 2020 |
| IPE Property Ltd | Real estate | 2026 |
| Ipexd Ltd | Professional & scientific | 2026 |
| Ipqi Ltd | Information & communication | 2026 |
| IRA Retail Ltd | Wholesale & retail | 2021 |
| Iridescent Ideas CIC | Professional & scientific | 2011 |
| Iris Visioncare Limited | Wholesale & retail | 2010 |