| Broxash Ltd | Other services | 2018 |
| BSR Childcare Nursery Limited | Health & social care | 2024 |
| Buckingham Canal Limited | Construction | 2020 |
| Bueno Ltd | Hospitality | 2016 |
| Build Influence Limited | Arts & recreation | 2026 |
| Building Heritage & Co Limited | Construction | 2024 |
| Building Services Solutions (Construction) Limited | Construction | 2018 |
| Buildwise Partners Ltd | Construction | 2025 |
| Bulbourne Consulting Ltd | Wholesale & retail | 2023 |
| Bulmer and Counter Architects Ltd | Professional & scientific | 2019 |
| Bump and Beyond Best Body for Pregnancy Ltd | Health & social care | 2022 |
| Burchnall Private Wealth Ltd | Administrative & support | 2026 |
| Burger Buzz Ltd | Hospitality | 2019 |
| Burnbury Advisory Limited | Professional & scientific | 2021 |
| Bursarnet Limited | Education | 2013 |
| Bustle and BOW Ltd | Wholesale & retail | 2020 |
| Busy Living Limited | Administrative & support | 2003 |
| Bvor Watches Limited | Wholesale & retail | 2021 |
| BWA Recruitment Specialist Ltd | Administrative & support | 2026 |
| BXT Consultants Limited | Professional & scientific | 2014 |
| BXW Consulting Ltd | Professional & scientific | 2023 |
| BY Design Creative Limited | Professional & scientific | 2022 |
| BY Kathryn Ltd | Manufacturing | 2011 |
| C & B Insurance Services Limited | Financial services | 2007 |
| C Deehan Commercial Services Ltd | Wholesale & retail | 2019 |
| C&S Building and Brickwork Ltd | Construction | 2018 |
| C&S Property and Investments Ltd | Real estate | 2024 |
| C.L.Taxation Personnel | | 1989 |
| Cadalor Ltd | Wholesale & retail | 2023 |
| Cahill Coaching and Consulting UK Limited | Administrative & support | 2014 |
| Caiborg Services Limited | Wholesale & retail | 2023 |
| Cain Auctions Ltd | Wholesale & retail | 2020 |
| Cain Property Services Ltd | Construction | 2020 |
| Callard House Limited | Real estate | 2015 |
| Calspring Limited | Real estate | 1969 |
| Campbell House International Limited | Administrative & support | 2017 |
| Camvergentob Ltd | Information & communication | 2019 |
| Canaglaze Limited | Construction | 2020 |
| Canal Lane Ltd | Construction | 2023 |
| Canalside (Berkhamsted) Management Limited | Real estate | 2001 |
| CAP Gate Ltd | Construction | 2025 |
| Capel Media Ltd | Information & communication | 2021 |
| Capell Construction Ltd | Construction | 2016 |
| Capo Sport Ltd | Information & communication | 2026 |
| Capuchin Limited | Administrative & support | 2019 |
| Capulet Ltd | Arts & recreation | 2023 |
| Car COW Limited | Wholesale & retail | 2024 |
| Cardiac Rehab Ltd | Health & social care | 2012 |
| Carl Lundberg LLP | | 2017 |
| Carlile Furniture Limited | Manufacturing | 2005 |
| Carlile Psychology Ltd | Health & social care | 2020 |
| Carloe Ltd | Real estate | 2025 |
| Carp Global Limited | Administrative & support | 2020 |
| Carpetmaster Contracts Ltd | Wholesale & retail | 2019 |
| Carter Resourcing Group Ltd | Administrative & support | 2026 |
| Carter Speech and Language Therapy Consultancy Ltd | Health & social care | 2014 |
| Cassacol Ltd | Real estate | 2023 |
| Castel Clothing Ltd | Wholesale & retail | 2026 |
| Castellain 194 Limited | Construction | 2022 |
| Castle 45 Holdings Limited | Financial services | 2024 |
| Castle Close Ltd | Construction | 2020 |
| Castle Hill Court (Berkhamsted) Management Limited | Households | 1975 |
| Castle Lawns Limited | Real estate | 2024 |
| Castle Planning Limited | Professional & scientific | 2015 |
| Castle Property Investments Limited | Financial services | 2022 |
| Castle REX 24 Limited | Real estate | 2022 |
| Castlemeade Homes Limited | Construction | 2004 |
| Castleton Consulting Limited | Professional & scientific | 1997 |
| Cat's Pajamas Communications Ltd | Professional & scientific | 2019 |
| CB Property Advisory Ltd | Professional & scientific | 2025 |
| CC Milan Coaching Co Ltd | Information & communication | 2018 |
| CDR Insights and Analytics Limited | Professional & scientific | 2015 |
| CEB Coaching Ltd | Professional & scientific | 2021 |
| Cecily (IP) Ltd | Administrative & support | 2024 |
| Cecily Day Spa Limited | Other services | 2018 |
| Cecily Marlow Ltd | Other services | 2021 |
| Cecily Retreats Marlow Ltd | Hospitality | 2023 |
| Cecily Spa Retreats Limited | Hospitality | 2023 |
| Cecily Spa Windsor Limited | Other services | 2023 |
| Cecily Ventures Ltd | Extraterritorial | 2021 |
| Cecily Windsor Ltd | Other services | 2026 |
| Celebrate the Corners Limited | Professional & scientific | 2010 |
| Cella Recruitment Ltd | Administrative & support | 2025 |
| Celosias Consulting Ltd | Professional & scientific | 2016 |
| Centurion BW Limited | Construction | 2018 |
| Certa Private Finance Limited | Financial services | 2020 |
| CES Electrics Limited | Construction | 2025 |
| Chalet Film Limited | Information & communication | 2024 |
| Chalets Marketing Limited | Administrative & support | 2010 |
| Chalk & Charcoal Limited | Manufacturing | 2015 |
| Change Management Technology Ltd | Information & communication | 2012 |
| Changing Minds Psychological Services LLP | | 2015 |
| Chaos Collaborative Ltd | Information & communication | 2022 |
| Charles Street Advisors Limited | Information & communication | 2024 |
| Charles Street Development Limited | Administrative & support | 2009 |
| Charles.Robinson Ltd | Energy | 2019 |
| Charlie Macey Coaching Limited | Education | 2026 |
| Charlotte Cliffe Medical Aesthetics Ltd | Other services | 2026 |
| Charlotte Love Garden Design Ltd | Administrative & support | 2015 |
| Chatto Consulting Ltd | Information & communication | 2022 |