| Cycling With US Ltd | Denmead Waterlooville | 2018 |
| Cycloc Limited | London | 2005 |
| Cyclopean Ltd | Wembley | 2018 |
| Cycure Ltd | London | 2022 |
| Cyferkon Limited | Harpenden | 2012 |
| Cyfor Limited | Manchester | 2005 |
| Cygna Limited | Bury St. Edmunds | 1996 |
| Cygnes Real Investments Ltd | London | 2020 |
| Cygnet Children's Home Ltd | Westcliff-On-Sea | 2018 |
| Cygnet Ltd | Godalming | 2015 |
| Cyklonix Limited | Stockport | 2001 |
| Cylinder Testing Services Limited | Warrington | 2008 |
| Cylvho International Ltd | Beckenham | 2016 |
| Cynbor Ingredients Ltd. | Kenilworth | 2014 |
| Cynergy Building Services Limited | London | 2022 |
| CYNERGY3 Components FAB Limited | Swindon | 2002 |
| Cynon Properties Limited | Ystradgynlais | 2012 |
| Cypher Printworks Limited | Cardiff | 2021 |
| Cypher Quantum Ltd | London | 2020 |
| Cypher Services Limited | | 1996 |
| Cyport Ltd | London | 2005 |
| Cypress 1969 Limited | Glasgow | 2014 |
| Cyprus American Hospital Limited | South Croydon | 2013 |
| Cyprus Aviation Academy Limited | South Croydon | 2014 |
| Cyprus Cola Ltd | London | 2022 |
| Cyprus Halloumi & Cheese Limited | South Croydon | 2008 |
| Cyprus International Airlines Limited | South Croydon | 2014 |
| Cyprus Wine Festival Limited | | 2004 |
| CYR Data Ltd | High Wycombe | 2021 |
| Cyril H.Lovegrove Limited | Sutton Coldfield | 1951 |
| Cyril Minns Limited | Bristol | 1982 |
| Cyril Norton & Sons (Plant) Limited | Swansea | 1999 |
| Cyril Sense Health Care Solutions Limited | Chatham | 2024 |
| Cyrus Ashley Junior Flash Limited | London | 2024 |
| Cystomed Ltd | Harlow | 2015 |
| Cythen Holdings Limited | Shrewsbury | 2023 |
| Cythen Limited | Shrewsbury | 2023 |
| Cywaith Cyfyngedig | Caernarfon | 2010 |
| Czarnowski Limited | Norwich | 2018 |
| Czechmade Limited | Luton | 1994 |
| Célere Ltd | Perth | 2022 |
| D & a (1859) Limited | London | 1995 |
| D & a (1860) Limited | London | 1995 |
| D & a Consultants (Mayfair) Ltd | London | 2010 |
| D & a Hill Limited | Huddersfield | 1999 |
| D & C (Dunswell) Limited | Beverley | 2011 |
| D & C Auto Services Ltd | Bristol | 2020 |
| D & D Elite Property Maintenance Limited | West Boldon | 2012 |
| D & G Family Law Ltd | Burnley | 2015 |
| D & G Holdings Limited | Coleford | 2006 |
| D & H Jewellers Limited | Sunderland | 2014 |
| D & H Travel Ltd | Darrington | 2013 |
| D & I Home Improvements Ltd | Barnsley | 2014 |
| D & I Rutherford (Holdings) Limited | Tain | 2005 |
| D & J Taylor Limited | West Yorkshire | 1998 |
| D & K Investment Management Ltd | Edinburgh | 2012 |
| D & K Lindop Holdings Limited | Deeside | 1980 |
| D & L Accountancy Services Ltd | Chelmsford | 2010 |
| D & L Higgins Limited | Harrow | 2015 |
| D & M (Property Management) Limited | Rowley Regis | 1996 |
| D & M Sales Limited | High Wycombe | 1992 |
| D & M Services (Pembs) Limited | Milford Haven | 2010 |
| D & P Electrical Systems Limited | Holmer Green | 2009 |
| D & P Property Management (Portsmouth) Ltd | Hampshire | 2007 |
| D & P VPP Ltd | Halesowen | 2009 |
| D & R Diagnostics Ltd | Bolton | 2023 |
| D & R Recycling Brokers Ltd | Bedlington | 2021 |
| D & S (Ryde) Holdings Limited | Ryde | 2013 |
| D & S Potter Ltd | Co Tyrone | 2006 |
| D & T Industrial Solutions Limited | Hereford | 2021 |
| D 2 Racing Limited | Chorley | 2010 |
| D 444 Limited | Oxford | 2022 |
| D a Ellis Design Services Ltd | Hebden Bridge | 2013 |
| D a English Roses Limited | Wolverhampton | 2017 |
| D and F Mechanical Limited | Hillingdon | 2019 |
| D B Foot Limited | Kingswinford | 2011 |
| D B Management Consultancy Ltd | Castleford | 2016 |
| D B Roberts Professional Services Ltd | Shrewsbury | 2016 |
| D B S Brand Factors Ltd | Basingstoke | 2001 |
| D B Sports Cars Ltd | Bristol | 2011 |
| D B Stuart (Southern) Limited | Falkirk | 2004 |
| D B Walker & Sons Limited | Saddleworth | 2019 |
| D Baker(Nursing) Ltd | Shenstone | 2016 |
| D Berry & Co (Holdings) Limited | Birmingham | 2011 |
| D Berry & Co (Pipe Fitting Supplies) Limited | Birmingham | 2011 |
| D Black Consultancy Limited | Belfast | 2023 |
| D Brook Limited | Leeds | 2017 |
| D Byrne Limited | Shipdham | 2010 |
| D C Jeffs Limited | Bicester | 2025 |
| D C M Wholesale Limited | Peterborough | 1986 |
| D C Precision Plant Limited | Leeds | 2016 |
| D D Security Services Limited | Kington | 2015 |
| D Damidavicius Fisk Limited | Cardiff | 2025 |
| D Diamond Limited | Birmingham | 2022 |
| D E Leece Limited | Sheffield | 2014 |
| D Electrics Ltd | Leeds | 2023 |
| D F M Nominees Limited | Epsom | 1987 |
| D Faulkner Limited | West Sussex | 1999 |
| D G Jones & Partners Limited | Slough | 2011 |
| D G Property Invest Limited | Colchester | 2024 |