| BYM Northampton Limited | Real estate | 2021 |
| BYO Nunhead Ltd | Wholesale & retail | 2021 |
| Byounic Limited | Information & communication | 2021 |
| Byrak Ltd | Wholesale & retail | 2024 |
| Byrekio Solutions Ltd | Administrative & support | 2020 |
| Byrne Bright Solutions Limited | Professional & scientific | 2015 |
| Byron Terrett Limited | Construction | 2018 |
| Byrshop Ltd | Wholesale & retail | 2025 |
| BYS Project Ltd | Information & communication | 2021 |
| Byset Design Limited | Professional & scientific | 1976 |
| Byte ME Limited | Information & communication | 1996 |
| Byte Path Flow Ltd | Information & communication | 2025 |
| Bytebuy Electronics Ltd | Manufacturing | 2025 |
| Bytecodejic Ltd | Information & communication | 2026 |
| Bytehorizon Limited | Information & communication | 2025 |
| Bytematrix Limited | Information & communication | 2025 |
| Bytemine Technologies Ltd | Information & communication | 2020 |
| Bytes Enterprises Ltd | Wholesale & retail | 2017 |
| Bytewises KRD Ltd | Information & communication | 2025 |
| Bythewheels Ltd | Wholesale & retail | 2026 |
| Byuk Housing Limited | Real estate | 2024 |
| BYW Community Ltd | Administrative & support | 2020 |
| Bzkim Limited | Wholesale & retail | 2025 |
| Bzvs Ltd | Wholesale & retail | 2023 |
| BZY Ltd | Real estate | 2019 |
| Bzycrispycardiff Ltd | Hospitality | 2025 |
| C & D Creative Engineering Ltd | Manufacturing | 2015 |
| C & F Stays Limited | Hospitality | 2026 |
| C & G P Associates Limited | Professional & scientific | 2005 |
| C & J Business Limited | Real estate | 2012 |
| C & J Leisure Ltd | Hospitality | 2009 |
| C & K Evans Jewellers Limited | Wholesale & retail | 2005 |
| C & M (SW) Ltd | Manufacturing | 2015 |
| C & M Site Management Limited | Construction | 2019 |
| C & N Commerce Ltd | Administrative & support | 2021 |
| C & RB Solutions Ltd | Hospitality | 2022 |
| C & S Salons Limited | Other services | 2018 |
| C &C Care UK Limited | Public administration | 2022 |
| C a B Property Limited | Real estate | 2018 |
| C a Brown Home Improvements Ltd | Construction | 2019 |
| C a Davies Ltd | Construction | 2025 |
| C a Pitt Ltd | Administrative & support | 2019 |
| C and J Maintenance (Cardiff) Ltd | Administrative & support | 2025 |
| C B Lewis Limited | Health & social care | 2025 |
| C B M N Properties Limited | Real estate | 2018 |
| C Bridges Contractors Ltd | Administrative & support | 2019 |
| C C Builds Ltd | Construction | 2024 |
| C C I T Engineering Solutions Limited | Administrative & support | 2023 |
| C Capital (London) Limited | Construction | 2017 |
| C Core Roofing Limited | Construction | 2026 |
| C D Bellamy Limited | Arts & recreation | 2006 |
| C D Fegan Limited | Health & social care | 2015 |
| C E Facilitate Ltd | Construction | 2025 |
| C E G Europe Limited | Financial services | 2012 |
| C E Jones CYF | Information & communication | 2021 |
| C E S (South Wales) Limited | Construction | 1996 |
| C Flint Services Ltd | Manufacturing | 2025 |
| C Forster TM Ltd | Other services | 2019 |
| C G White Limited | Wholesale & retail | 2018 |
| C H O Contracting Limited | Professional & scientific | 2015 |
| C Harry Properties Ltd | Real estate | 2022 |
| C Hobbins Financial Solutions Ltd | Financial services | 2012 |
| C J Autocentre Limited | Wholesale & retail | 2012 |
| C J Fenton Limited | | 2019 |
| C J Hannan Ltd | Financial services | 2012 |
| C J Newby Services Limited | Health & social care | 2006 |
| C J OIL & GAS Limited | Professional & scientific | 2014 |
| C James Carpentry & Construction Ltd | Construction | 2021 |
| C K Associate Painting Limited | Construction | 2025 |
| C K Chan Limited | Wholesale & retail | 2012 |
| C K Communications Limited | Information & communication | 1997 |
| C L Autos Limited | Administrative & support | 2009 |
| C Lewis Construction Ltd | Construction | 2017 |
| C M Clee Consultancy Ltd | Professional & scientific | 2019 |
| C Marine Boat Sales Ltd | Wholesale & retail | 2023 |
| C Marston Ltd | Information & communication | 2017 |
| C Maunder Dental Services Ltd | Health & social care | 2023 |
| C Mcmahon Management Ltd | Professional & scientific | 2020 |
| C Mgmnt Services Ltd | Administrative & support | 2012 |
| C R Electrics (SW) Limited | Construction | 2014 |
| C R Tutorials LLP | | 2019 |
| C S Dean Group Limited | Financial services | 2021 |
| C Sharp Strategy Limited | Information & communication | 2015 |
| C Sounds Limited | Information & communication | 2023 |
| C Sportswear Ltd | Wholesale & retail | 2020 |
| C Tebby Ltd | Construction | 2019 |
| C Two Caterings Limited | Hospitality | 2015 |
| C W Contractors Limited | Construction | 2018 |
| C Young Advisory Limited | Professional & scientific | 2025 |
| C&A Car Repairs Ltd | Wholesale & retail | 2018 |
| C&A Cardiff Ltd | Wholesale & retail | 2022 |
| C&A Dentexpert Limited | Health & social care | 2017 |
| C&C Developments NE Ltd | Construction | 2025 |
| C&C Freight Limited | Transport & logistics | 2018 |
| C&C Joinery Specialists Limited | Construction | 2023 |
| C&C Sweets Limited | Hospitality | 2021 |
| C&E Amery Limited | Other services | 2016 |
| C&E Associates Ltd | Administrative & support | 2024 |
| C&F Halifax Ltd | Hospitality | 2018 |
| C&G Construction Ltd | Construction | 2023 |