| Bmjs Tax Ltd | Professional & scientific | 2016 |
| Bodoni Systems Limited | Information & communication | 1990 |
| Bona Food Limited | Hospitality | 2025 |
| Bondi Limited | Administrative & support | 2013 |
| Bonnyknox Solar Limited | Energy | 2025 |
| Booth Visuals Limited | Information & communication | 2026 |
| Borrow My Garden Limited | Information & communication | 2019 |
| Botein Bess Ltd | Professional & scientific | 2020 |
| Bovingdon Grange (Herts) Resident Management Company Limited | Households | 2024 |
| Bovingdon Grange Block 1 Residents Management Company Limited | Households | 2025 |
| Boxted Energy Limited | Energy | 2024 |
| Bozo Film Ltd | Information & communication | 2025 |
| Bracey's Accountants (Hemel Hempstead) Limited | Professional & scientific | 2015 |
| Bradbury Cottages Ltd | Real estate | 2023 |
| Bradshaw Interiors Limited | Construction | 2014 |
| Braich DDU Limited | Energy | 2011 |
| Brainwave Studios Ltd | Information & communication | 2024 |
| Brasier Freeth LLP | | 2006 |
| Brewster Plumbing & Heating Services Ltd | Construction | 2015 |
| Brickworth Developments Limited | Construction | 1963 |
| Bridgehead Consultancy Limited | Professional & scientific | 2019 |
| British Contracts Company Limited | Extraterritorial | 1920 |
| Bromet Close (Nascot Croft) Residents Association Limited | Households | 1996 |
| Bromet Close (Watford) Amenities Association Limited | Households | 1962 |
| Bron Coys Energy Storage Limited | Energy | 2022 |
| Brookson (5694Q) Limited | Administrative & support | 2007 |
| BT Mortgages Limited | Financial services | 2021 |
| BUA Properties Ltd | Real estate | 2021 |
| Bucks Groundwork Developments Ltd | Construction | 2014 |
| Bunsen Communications Ltd | Professional & scientific | 2016 |
| Burnthouse Farm Limited | Energy | 2012 |
| Bushey Accounting Services Ltd | Professional & scientific | 2018 |
| Bushey GAS Limited | Construction | 2005 |
| Butler & Daughters Real Estate Ltd | Real estate | 2025 |
| Butterfly Property Developments Limited | Real estate | 2020 |
| BWF Retail Ltd | Manufacturing | 2021 |
| C & C Elvin Properties Ltd | Construction | 2003 |
| Caenstone Ltd | Financial services | 2018 |
| Cairn Duhie Energy Limited | Energy | 2022 |
| Calculus Accounting Services Ltd | Professional & scientific | 2018 |
| Calculus IT & Book-Keeping Services Limited | Professional & scientific | 2011 |
| Calibre Group Holdings Limited | Financial services | 2024 |
| Calibre Precision Climate Control Limited | Administrative & support | 2019 |
| Calm Charging Group Limited | Energy | 2023 |
| Calm Charging Limited | Energy | 2023 |
| Campbell & Syme Ltd | Manufacturing | 2017 |
| Candle Land Ltd | Manufacturing | 2025 |
| Capeford Developments Limited | Real estate | 2025 |
| Capella Bess Ltd | Professional & scientific | 2021 |
| Capital Services (Holdings) Limited | Financial services | 2014 |
| Capital Services (Kings Langley) Limited | Construction | 2014 |
| Capital Services (Topco) Limited | Financial services | 2020 |
| Capital Sky Demolition Limited | Construction | 2022 |
| Capital Sky Group Limited | Construction | 2024 |
| Capital Sky Holdings Limited | Financial services | 2022 |
| Capital Sky Limited | Water & waste | 2015 |
| Capital Sky Plant Limited | Administrative & support | 2022 |
| Capital Sky Properties Limited | Extraterritorial | 2022 |
| Carbon Free Ltd | Extraterritorial | 2008 |
| Carbon Free Neilston Ltd | Energy | 2009 |
| Carbon Nutrition Limited | Health & social care | 2024 |
| Cardiff Gate Business Park Limited | Construction | 1991 |
| Cardiff Gate Management Limited | Real estate | 1995 |
| Carscreugh Renewable Energy Park Limited | Energy | 2006 |
| Cart & Horses Ltd | Hospitality | 2026 |
| Casa Russo Limited | Professional & scientific | 2001 |
| Castle Pill Wind Limited | Energy | 2013 |
| Castlehill Enterprises Limited | Professional & scientific | 2025 |
| Cbfi Investment Limited | Financial services | 2017 |
| CCS (Herts) Ltd | Wholesale & retail | 2024 |
| CD Bridgeman Supervisory Services Limited | Construction | 2014 |
| CDM Estimating Ltd | Professional & scientific | 2026 |
| CDR Consulting Limited | Information & communication | 2021 |
| CDR Evolution Ltd | Professional & scientific | 2017 |
| Century Engineering and Refrigeration Installations Limited | Construction | 1985 |
| Chak Rogers Carpentry Ltd | Manufacturing | 2024 |
| Chalgrove Solar Limited | Energy | 2013 |
| Channel Tools Holdings Limited | Administrative & support | 2022 |
| Channel Tools Limited | Information & communication | 2010 |
| Charlie George Rigging Services Ltd | Information & communication | 2015 |
| Chayipan Security Services Ltd | Administrative & support | 2018 |
| Chess Valley Roofing & Construction Ltd | Construction | 2026 |
| Chime Software Limited | Information & communication | 2017 |
| Chimmens Energy Limited | Energy | 2022 |
| Chimp Consulting Ltd | Professional & scientific | 2026 |
| Chipless FP Ltd. | Construction | 2021 |
| Chipperfield Accounting Ltd | Professional & scientific | 2013 |
| Chipperfield Clarendon Cricket Club Limited | Arts & recreation | 2020 |
| Chipperfield Corinthians Football Club Limited | Arts & recreation | 2022 |
| Chipperfield Corinthians Youth Football Club Ltd | Arts & recreation | 2017 |
| Chipperfield Events CIC | Arts & recreation | 2023 |
| Chipperfield Mews Ltd | Households | 2018 |
| Chipro Car Company Limited | Wholesale & retail | 2015 |
| Chiptuningshop Ltd | Wholesale & retail | 2012 |
| Chirita Construction Ltd | Construction | 2018 |
| Choc & Peanut Ltd | Wholesale & retail | 2023 |
| Churchfield Estates Ltd | Real estate | 2016 |
| Churchtown Farm Solar Limited | Energy | 2011 |
| Cinnamond Plant Limited | Construction | 1972 |
| Circleace Ltd | Wholesale & retail | 2025 |