| Ironhurst Ltd | Administrative & support | 2026 |
| Ironoak Advisory Ltd | Professional & scientific | 2023 |
| Ironsides Protector Limited | Financial services | 2012 |
| Irresistible Health and Social Care Ltd | Health & social care | 2022 |
| Irresistible Healthcare Services Ltd | Health & social care | 2022 |
| Irsha Limited | Construction | 2005 |
| Irving Environmental Services Ltd | Professional & scientific | 2019 |
| Irwell Power Limited | Energy | 2016 |
| IS Bristol Limited | Hospitality | 2021 |
| IS Global Consulting Limited | Professional & scientific | 2026 |
| ISA Catarina Orthodontics Ltd | Health & social care | 2023 |
| Isaacs School of Motoring Ltd | Extraterritorial | 2020 |
| Isabel Ball Limited | Health & social care | 2016 |
| Isabelle Enterprises Ltd | Real estate | 2022 |
| Isami Ltd | Health & social care | 2025 |
| Isati Engineering Solutions Limited | Professional & scientific | 2021 |
| Isatou Care Ltd | Health & social care | 2019 |
| Isbilya Health Ltd | Health & social care | 2025 |
| Isbury Ltd | Professional & scientific | 2025 |
| Isc.Trade Ltd | Wholesale & retail | 2012 |
| Isca Consulting Limited | Professional & scientific | 2023 |
| Ise.Yu Limited | Professional & scientific | 2026 |
| Isgah Limited | Other services | 2018 |
| Ishtar Ltd | Hospitality | 2022 |
| Ishtiaq Engineering Services Ltd | Professional & scientific | 2019 |
| Isidore Ltd | Extraterritorial | 2015 |
| Isidoro Verification Solutions Ltd | Information & communication | 2016 |
| Isig Healthcare Group Private Ltd | Health & social care | 2025 |
| Isinbar Ltd | Hospitality | 2018 |
| Isintu Trends Ltd | Hospitality | 2022 |
| Isiras Ltd | Professional & scientific | 2019 |
| Isis Blake Ltd | Arts & recreation | 2025 |
| Isitt Ltd | Extraterritorial | 2008 |
| Iskara Company LP | | 2012 |
| Iskcon Bristol Ltd | Health & social care | 2025 |
| Iskra Enterprises Limited | Professional & scientific | 1993 |
| ISL Recruitment Limited | Administrative & support | 2011 |
| Isla Giovanna Ltd | Wholesale & retail | 2021 |
| Isla MAX Ltd | Real estate | 2016 |
| Islam in Bristol Ltd | Wholesale & retail | 2018 |
| Island Planning Limited | Professional & scientific | 2024 |
| Island Ropes & Rigging Limited | Manufacturing | 2018 |
| Island Seekers Limited | Arts & recreation | 1987 |
| Island Traders Limited | Wholesale & retail | 2018 |
| Islaskye Productions Ltd | Information & communication | 2021 |
| Isle of Wedmore Construction Limited | Construction | 2007 |
| Isle Veterinary Group Limited | Extraterritorial | 2010 |
| Isleworth Shipping Company Limited | Real estate | 2000 |
| Ismail Clark Properties Limited | Real estate | 2024 |
| Isme Recruitment Limited | Administrative & support | 2017 |
| Ismi Developments Ltd | Real estate | 2026 |
| Ismi Properties Ltd | Real estate | 2019 |
| Ismwm Limited | Health & social care | 2026 |
| Isn'T Limited | Professional & scientific | 2015 |
| Isolutions Software Ltd | Information & communication | 2023 |
| Isomatrix Limited | Information & communication | 2020 |
| Ison Security & Training Ltd | Administrative & support | 2021 |
| Isotrans Ltd | Transport & logistics | 2025 |
| Isquare Property Management Ltd | Real estate | 2020 |
| ISR Severn Land Management Ltd | Construction | 2025 |
| Israelites Ltd | Information & communication | 2014 |
| ISS Interiors Ltd | Construction | 2014 |
| Issa-Rae Limited | Health & social care | 2019 |
| Issacukedd Limited | Transport & logistics | 2022 |
| IST Reading Limited | Information & communication | 1988 |
| Istanbul Barbers HS Ltd | Other services | 2024 |
| Istanbul Grill Mezze Ltd | Hospitality | 2018 |
| Istanbul Mini Market Ltd | Wholesale & retail | 2019 |
| Istay Property Limited | Construction | 2018 |
| Isteni Constructions & Consultants Ltd | Construction | 2023 |
| Isteni Design & Build Ltd | Construction | 2026 |
| Isteni Management Limited | Real estate | 2023 |
| Istone Masonry Ltd | Manufacturing | 2025 |
| Istusgrand Developments Limited | Construction | 1966 |
| Isundunrin Ltd | Health & social care | 2021 |
| Isupplyhubb Ltd | Information & communication | 2025 |
| Isurv Engineering Services Ltd | Construction | 2018 |
| IT and Marketing Solutions Limited | Information & communication | 2007 |
| IT Assets International Ltd | Wholesale & retail | 2023 |
| IT Business Merchant Ltd | Transport & logistics | 2016 |
| IT Solutions & Telecoms Ltd | Information & communication | 2018 |
| IT Solutions Bristol Ltd | Information & communication | 2021 |
| IT Technologic Solutions Ltd | Information & communication | 2025 |
| IT Trans Consulting Limited | Information & communication | 2020 |
| It's in the BAG Cancer Support Ltd. | Health & social care | 2015 |
| IT, Science Consulting & Research Ltd | Information & communication | 2011 |
| Itaa Property's Ltd | Real estate | 2026 |
| Italb Ristorante Ltd | Hospitality | 2018 |
| Italgust Ltd | Hospitality | 2024 |
| Italia & Styl Ltd | Construction | 2018 |
| Italian Contrast Ltd | Information & communication | 2025 |
| Italian Cuisini I.T Restaurant Ltd | Hospitality | 2024 |
| Italian Food Bristol Ltd | Hospitality | 2021 |
| Italian Takeaway Ltd | Hospitality | 2013 |
| Italic Marketing Ltd | Extraterritorial | 2009 |
| Italmatch UK Limited | Manufacturing | 2007 |
| Italy First Choice Ltd | Administrative & support | 2010 |
| Italy Solar Generation One Limited | Energy | 2018 |
| ITB Pension Trustee Limited | Professional & scientific | 2022 |
| ITB Pension Trustees (1) Limited | Professional & scientific | 2010 |