| Iroko Properties Limited | Real estate | 2021 |
| Irwin Group Limited | Financial services | 2019 |
| Irwin Holdings Limited | Real estate | 2016 |
| Isactrans Ltd | Transport & logistics | 2021 |
| Isca Medical Services Limited | Health & social care | 2022 |
| Iscootbike Ltd | Arts & recreation | 2018 |
| Isdg Limited | Information & communication | 2013 |
| Island Court Looe Limited | Households | 2014 |
| Island Lodge Hostel Ltd | Hospitality | 2019 |
| Island Vybz Records Ltd | Information & communication | 2025 |
| Islandcrescent Limited | Hospitality | 2014 |
| Isoboh UK Ltd | Wholesale & retail | 2021 |
| Issus Limited | Professional & scientific | 2007 |
| Istanbul Barber Plymouth New Ltd | Other services | 2024 |
| Istanbul Barbers Plympton Ltd | Other services | 2024 |
| Istdp South West Limited | Health & social care | 2024 |
| IT IS Architecture Limited | Professional & scientific | 2003 |
| IT Takes a Village Plymouth CIC | Wholesale & retail | 2024 |
| Itah Garden Supplies Ltd | Manufacturing | 2021 |
| ITD Research Ltd | Other services | 2010 |
| ITG Consulting Limited | Information & communication | 2024 |
| Itriplea (Freehold) Ltd | Real estate | 2026 |
| Itriplea Holdings Ltd | Real estate | 2026 |
| ITS a Haigh Thing Ltd | Real estate | 2023 |
| ITS Possible Ltd | Education | 2010 |
| Ivor Dewdney's Pasties Limited | Wholesale & retail | 1998 |
| Ivory Fusion Ltd | Other services | 2020 |
| IVY Property Investments Ltd | Information & communication | 2022 |
| Ivybridge Accountants Limited | Professional & scientific | 2013 |
| Ivybridge Carpets Limited | Wholesale & retail | 2022 |
| Ivybridge Electrical Solutions Ltd | Professional & scientific | 2024 |
| Ivybridge Trade Centre Limited | Wholesale & retail | 2010 |
| Iwch Developments Ltd | Construction | 2013 |
| Iwiqyn Ltd | Education | 2026 |
| Iwsw Property Ltd | Households | 2020 |
| Iyanar Stores Ltd | Wholesale & retail | 2025 |
| Iyanu Ventures UK Limited | Wholesale & retail | 2026 |
| J & D Bricklaying Contractors Limited | Construction | 2005 |
| J & I Car Sales Ltd | Wholesale & retail | 2014 |
| J & J Beach Cafe Ltd | Hospitality | 2015 |
| J & M Lightyear Logistics Ltd | Transport & logistics | 2021 |
| J & R Kneebone Tree Care LLP | | 2016 |
| J & S Plymouth Limited | Hospitality | 2024 |
| J & S PUB Group Ltd | Hospitality | 2025 |
| J & T Plymouth Ltd | Real estate | 2016 |
| J and J Land Limited | Construction | 2017 |
| J and S Damp Proofing and Construction Limited | Construction | 2014 |
| J B Couriers (SW) Limited | Transport & logistics | 2025 |
| J Barrow Transport Limited | Transport & logistics | 2016 |
| J Burnett Construction Ltd | Construction | 2025 |
| J Clifton Plumbing & Heating Limited | Construction | 2011 |
| J D Builders Services Ltd | Construction | 2023 |
| J D Racing Limited | Wholesale & retail | 2010 |
| J Dog Grooms Ltd | Other services | 2021 |
| J E Financial Solutions Limited | Professional & scientific | 2017 |
| J Elect Limited | Health & social care | 2024 |
| J French Security Consultant Ltd | Administrative & support | 2014 |
| J Herbert Holdings Ltd | Real estate | 2020 |
| J J Barbers Ltd | Other services | 2015 |
| J J Freehold Ltd | Real estate | 2026 |
| J J L (SW) Ltd | Health & social care | 2020 |
| J J P Landscaping Services Limited | Administrative & support | 2024 |
| J J Rainbow Properties Ltd | Hospitality | 2025 |
| J J Security & Maintenance Ltd | Construction | 2018 |
| J K Liftservices Ltd | Manufacturing | 2020 |
| J Keating Limited | Construction | 2026 |
| J Killman Transport Limited | Information & communication | 2004 |
| J L Jones Watch Boxes Ltd | Wholesale & retail | 2025 |
| J N E Construction Limited | Construction | 1990 |
| J Nickels Ltd | Wholesale & retail | 2007 |
| J P Nate Limited | Households | 2011 |
| J Perkins Construction Ltd | Construction | 2025 |
| J R Construction and Groundworks Ltd | Construction | 2023 |
| J R E&P Consultants Ltd | Professional & scientific | 2019 |
| J R Hall Agri Engineers Ltd | Professional & scientific | 2018 |
| J Reid Electrical Ltd | Construction | 2019 |
| J Rogers Decorators Limited | Construction | 2017 |
| J S Murrain & Sons Limited | Construction | 2005 |
| J Shepherd & Sons Ltd | Real estate | 2021 |
| J Stone Bricklaying Limited | Construction | 2023 |
| J T Building Services Limited | Construction | 2005 |
| J Thompson Electrical Ltd | Construction | 2018 |
| J Warne Holdings Limited | Financial services | 2024 |
| J Y House Limited | Hospitality | 2017 |
| J&A Cleaning Services Ltd | Administrative & support | 2026 |
| J&B's Mini Market Ltd | Wholesale & retail | 2024 |
| J&C Healthcare Ltd | Health & social care | 2021 |
| J&Cwholesale Ltd | Wholesale & retail | 2026 |
| J&I Service and Repair Centre Ltd | Wholesale & retail | 2020 |
| J&J Joinery Solutions Ltd | Construction | 2025 |
| J&K Roofing & Building Maintenance Ltd | Construction | 2025 |
| J&L Developments Ltd | Real estate | 2016 |
| J&T Inns Ltd | Hospitality | 2018 |
| J-Supplied Ltd | Wholesale & retail | 2018 |
| J-Tec Carpentry Ltd | Construction | 2025 |
| J. J,Clothing Ltd | Wholesale & retail | 2024 |
| J. Jenkins Limited | Construction | 1984 |
| J. Taylor Ltd | Wholesale & retail | 2001 |
| J.A. Sharland Ltd | Construction | 2003 |
| J.A.H Electrical Services Limited | Other services | 2007 |