| Claudiu Rail Limited | London | 2017 |
| Claudwave Solutions Ltd | London | 2026 |
| Claughton Furniture Limited | North Ferriby | 2017 |
| Claus Marsh Ltd | Potters Bar | 2011 |
| Clavecins Sans Frontières Ltd | Lewes | 2024 |
| Clavell & Hind Limited | Cheltenham | 2022 |
| Claverham Group Limited | Solihull | 1997 |
| Claverham Limited | Solihull | 1997 |
| Claverhouse Fabrications Ltd | Dundee | 2017 |
| Claverton Cloches Limited | Frome | 2021 |
| Clavey Limited | Beds | 2005 |
| Clavius Tech Limited | Birmingham | 2023 |
| Claw Industries Ltd | Wimborne | 2025 |
| Claws N' Roars Ltd | Lampeter | 2024 |
| Claxo Ltd | Newton Stewart | 2020 |
| Claxton Cabinetry Ltd | Blandford Forum | 2021 |
| Claxton Community CIC | Kettering | 2025 |
| Claxton Composites Limited | Delabole | 2013 |
| Claxton Group Ltd | London | 2026 |
| Clay & Abbott Limited | Sutton Coldfield | 1996 |
| Clay and Co Newbury Ltd | Newbury | 2025 |
| Clay and Grain Limited | Ellon | 2025 |
| Clay and Jewel Ltd | Bolton | 2021 |
| Clay Club JCC Limited | London | 2024 |
| Clay Club LDN Limited | Hemel Hempstead | 2025 |
| Clay Club Skincare Limited | Cheltenham | 2018 |
| Clay Connect Art Ltd | Cambridge | 2024 |
| Clay Kobo Limited | London | 2025 |
| Clay MAC Ltd | Heskin | 2015 |
| Clay Medical Limited | London | 2026 |
| Clay Rebels Ltd | Stratford Upon Avon | 2021 |
| Clay-Zy Day Studio Limited | Nantwich | 2024 |
| Claybloom Ltd | Kington | 2025 |
| Claydon Precision Machining Limited | Ipswich | 1988 |
| Claydon Yield-O-Meter Limited | Newmarket | 1981 |
| Clayfield and Hall Limited | Leicestershire | 1939 |
| Clayhouse Interiors Ltd | Brighouse | 2017 |
| Claylite Aggregates Limited | Worksop | 2000 |
| Claymills Process Pipework & Fabrications Ltd | Burton On Trent | 2024 |
| Claymore Dairies Limited | Nairn | 2010 |
| Claymore Industries Limited | Glasgow | 2026 |
| Claymore Lock and Safe Company Limited | East Lothian | 2001 |
| Claymore Marine Ltd | Derby | 2014 |
| Claymore Trades Ltd | Glasgow | 2024 |
| Claymore Windows Limited | Claverhouse Industrial Park | 2005 |
| Claymores of London Limited | London | 2011 |
| Claypack Limited | Peterborough | 1971 |
| Clayphan Welding & Fabrication Limited | Lowestoft | 2024 |
| Claypool Limited | Halesowen | 2008 |
| Clays Farm Vintage Cider Ltd | Cinderford | 2022 |
| Clays Ltd. | Bungay | 1938 |
| Clayspoon Limited | Eastbourne | 2016 |
| Claystapling Limited | Dumfries | 1998 |
| Clayton & Co.(Penistone),Limited | Sheffield | 1933 |
| Clayton Aniline Company Limited | Farnborough | 1897 |
| Clayton Carpentry Limited | Hindhead | 2013 |
| Clayton Classic Cars Limited | Leamington Spa | 2017 |
| Clayton Commercial Properties Limited | Preston | 2009 |
| Clayton Contract Upholstery Limited | Lancashire | 2003 |
| Clayton DJ Equipment Ltd | London | 2026 |
| Clayton Engineering (UK) Limited | Derby | 2011 |
| Clayton Engineering Limited | Poole | 1976 |
| Clayton Equipment Limited | Birmingham | 2004 |
| Clayton Glass Limited | Stanley | 2004 |
| Clayton Locomotives Limited | Retford | 2025 |
| Clayton Park Bakery Limited | Preston | 2000 |
| Clayton Penistone Group Limited | Sheffield | 2013 |
| Clayton Polymers Ltd | Hove | 2014 |
| Clayton Portable Buildings Limited | Bradford | 1962 |
| Clayton Precision Engineering Co. Ltd. | Isleworth | 1999 |
| Clayton Project Engineering Limited | Sheffield | 2001 |
| Clayton Rail Equipment Limited | Coventry | 2025 |
| Clayton Stone Company Ltd | Saltaire | 2015 |
| Clayton Thermal Processes Limited | Warley | 1988 |
| Clayton Thermal Products Limited | Runcorn | 1978 |
| Clayton VS Limited | Burnsall Road | 1988 |
| Claytonautomation Ltd | Long Eaton | 2021 |
| Claytons Dairy Company Limited | Nantwich | 2014 |
| Clayworks Limited | Helston | 2002 |
| CLB Aircraft Engineer Ltd | Wigan | 2019 |
| CLB Cleanequip Ltd | Leicester | 2012 |
| CLB Duct Works Limited | Leicester | 2023 |
| CLB Plumbing Ltd | Bedford | 2023 |
| CLB Refrigeration Ltd | Tilbury | 2004 |
| CLC (UK) Limited | Stourbridge | 2001 |
| CLC Construction Ltd | Redhill | 2025 |
| CLC Couture & Aesthetics Ltd | Luton | 2023 |
| CLC Events Limited | Hitchin | 2025 |
| CLC Fabrications Ltd | Oakham | 2023 |
| CLC Sussex Limited | Burgess Hill | 2018 |
| CLC Utilities Limited | Wallsend | 2018 |
| Clcessex Ltd | Wickford | 2021 |
| Clcprints Ltd | Wickford | 2025 |
| CLD Electrical Ltd | Colchester | 2025 |
| CLD Fabrications Limited | Hessle | 2015 |
| Cleamax Engineering Limited | St. Albans | 2002 |
| Clean & Co Maintenance and Hygiene Limited | London | 2023 |
| Clean 'N' Jerk Limited | Grimsby | 2024 |
| Clean @ CUT Limited | Worksop | 2015 |
| Clean Air Limited | Bolton | 1994 |