| Numore Developments Limited | Extraterritorial | 2010 |
| Nurek Contractors Limited | Wholesale & retail | 1999 |
| Nurture Knowledge Ltd | Education | 2025 |
| Nurturing Beginnings Limited | Health & social care | 2022 |
| NUT Hill Accounting Services Limited | Professional & scientific | 2017 |
| Nuthill Reserve Limited | Households | 2021 |
| Nutrition Triathlon Limited | Education | 2020 |
| Nutrition X Limited | Health & social care | 2014 |
| Nuview Holdings Limited | Financial services | 2025 |
| Nuvioo Ltd | Wholesale & retail | 2025 |
| Nuvola Macchina Consulting Ltd | Information & communication | 2025 |
| NVC Holdings Limited | Professional & scientific | 2016 |
| NW Project Solutions Limited | Other services | 2009 |
| Nwpc Limited | Professional & scientific | 1935 |
| NWT Wheel Refurb Ltd | Wholesale & retail | 2021 |
| NXS Limited | Water & waste | 1999 |
| NXT Level Solutions Ltd | Professional & scientific | 2020 |
| NYI Group Ltd | Other services | 2026 |
| Nyland's Media Ltd | Administrative & support | 2016 |
| Nypton Ltd | Administrative & support | 2021 |
| Nysa Pharma Consulting Ltd | Professional & scientific | 2018 |
| NYT Investment Company Limited | Real estate | 2024 |
| O & H Mechanical Ltd | Construction | 2018 |
| O & T Developments Limited | Real estate | 2006 |
| O Bajo Limited | Health & social care | 2016 |
| O H Dean Ltd | Real estate | 2023 |
| O'Brien Supply Collective Ltd | Wholesale & retail | 2026 |
| O'Flynn (LS) Ltd | Professional & scientific | 2021 |
| O.C.S.C Ltd | Manufacturing | 2024 |
| O.C.U. (Gloucestershire) Limited | Administrative & support | 1994 |
| Oak & Stone Ltd | Construction | 2005 |
| Oak Green Property (SW) Ltd | Real estate | 2025 |
| Oak Manor (Cheltenham) Limited | Households | 1985 |
| Oak Security Consulting Limited | Information & communication | 2016 |
| Oak Tree Building Contractors Ltd | Construction | 2026 |
| Oakbank Residents Limited | Extraterritorial | 2015 |
| Oakfield Residents (the Park, Cheltenham) Limited | Households | 1978 |
| Oaklands Property Developments Ltd | Construction | 2020 |
| Oakleaze UK Ltd | Professional & scientific | 2005 |
| Oakley Improvements Ltd | Construction | 2023 |
| Oakmore Broker Network Limited | Financial services | 2025 |
| Oakridge (Abbeydale) Management Company Limited | Households | 1988 |
| Oaksmith Building Ltd | Construction | 2023 |
| Oakwood Drive Flats (12-22) Residents Association Limited | Households | 1977 |
| Oakwood Drive Flats (40-50) Management Company Limited | Households | 1992 |
| Oarga Services Ltd | Health & social care | 2022 |
| Oasis Balm Limited | Health & social care | 2025 |
| Oasis Habitats Developments Ltd | Professional & scientific | 2021 |
| OB Electric Control Systems Limited | Manufacturing | 2021 |
| Obyone Ltd | Transport & logistics | 2025 |
| Ocean View Terrace Management Company Limited | Households | 2018 |
| OCH Tech Ltd | Wholesale & retail | 2023 |
| Ochre Fire Design Ltd | Professional & scientific | 2025 |
| Octavian Developments Ltd | Construction | 2026 |
| Octo Property Solutions Ltd | Real estate | 2025 |
| Oculus Wealth Management (Cotswolds) Limited | Financial services | 2015 |
| Ocvr Ltd | Professional & scientific | 2025 |
| Odaanp Limited | Financial services | 2022 |
| ODG Homes Ltd | Real estate | 2025 |
| Odin Training Services Ltd | Education | 2025 |
| Odon Holding Ltd | Professional & scientific | 2020 |
| Odos Business Solutions Limited | Information & communication | 2016 |
| ODW Properties Ltd | Real estate | 2024 |
| Odys Investment Ltd | Real estate | 2023 |
| OE Management Limited | Hospitality | 2023 |
| OFF Spaces Limited | Construction | 2025 |
| Office Emporium Ltd | Wholesale & retail | 2026 |
| Officenet Systems Limited | Information & communication | 2001 |
| Offtrnd Limited | Wholesale & retail | 2021 |
| OFI Builders (Stroud) Limited | Real estate | 2018 |
| OFI Builders Limited | Administrative & support | 2017 |
| OG Carbon Works Ltd | Manufacturing | 2025 |
| Ogati Tyres Limited | Wholesale & retail | 2024 |
| OGG Group Ltd | Financial services | 2023 |
| OH Lets Ltd | Real estate | 2025 |
| OH1 Electrical Ltd | Manufacturing | 2023 |
| Ohisky’S Signatures N More Limited | Hospitality | 2026 |
| Ohmega Engineering Solutions Ltd | Professional & scientific | 2026 |
| OIL of Joy Ministry Ltd | Other services | 2025 |
| OJ Building Contractors Ltd | Construction | 2016 |
| OJ Film Productions Ltd | Information & communication | 2025 |
| OKO OTO Ltd | Wholesale & retail | 2023 |
| Olaston Ltd | Transport & logistics | 2020 |
| Olbas Limited | Manufacturing | 1995 |
| Old & New Developments Ltd | Real estate | 2022 |
| Old Bowling Green Management Company Limited | Households | 1972 |
| Old School Buildings Management Limited | Households | 1992 |
| Old Skool Ltd | Real estate | 2004 |
| Old Town Christian Trust | Financial services | 2012 |
| Old Town Pizza Ltd | Hospitality | 2022 |
| Oldridge & Hobbs Ltd | Arts & recreation | 2015 |
| Olia Consultancy Ltd | Professional & scientific | 2016 |
| Olive Link Limited | Health & social care | 2025 |
| Olive Tree Learning Limited | Education | 2013 |
| Oliver Wight Eame LLP | | 2002 |
| Oliver Wight U.K. Limited | Professional & scientific | 1990 |
| Oliver Wronski Wealth Management Ltd | Administrative & support | 2014 |
| Oliver's Bar Group Ltd | Hospitality | 2025 |
| Oliver's Gloucester Ltd | Hospitality | 2025 |
| Oliveret Limited | Professional & scientific | 2015 |