| Clemson's Haulage Ltd | Transport & logistics | 2021 |
| Clive Wicks Architects Limited | Construction | 1989 |
| Clockpelter Mews Management Company Limited | Households | 1989 |
| CM Agriculture (Lincolnshire) Limited | Agriculture & fishing | 2019 |
| CMB Construction & Communications Limited | Construction | 2003 |
| CMF Testing Ltd | Construction | 2014 |
| Cmkr Jackson Ltd | Real estate | 2026 |
| CN Plastering School Limited | Construction | 2025 |
| Cockapoo & Co Ltd | Other services | 2020 |
| Coding Ideas Ltd | Information & communication | 2013 |
| Colin Ward Funeral Services Limited | Other services | 2013 |
| Collect and Recycle Ltd | Water & waste | 2019 |
| Collingwood Ventures & Consulting Limited | Information & communication | 2026 |
| Collishaw & Kelly Property Solutions Ltd | Construction | 2025 |
| Collishaw Property Solutions Limited | Real estate | 2022 |
| Colsterworth Poultry Co.Limited | Agriculture & fishing | 1960 |
| Commercial Labour Solutions Ltd | Wholesale & retail | 2022 |
| Compass Point (Market Harborough) Management Company Limited | Real estate | 2006 |
| Computer Craig Limited | Information & communication | 2012 |
| Comutiq Ltd | Professional & scientific | 2019 |
| Conehead Management Limited | Administrative & support | 2009 |
| Conlon West Africa Limited | Mining & quarrying | 2010 |
| Conscius Medical Ltd | Health & social care | 2025 |
| Consultika Limited | Professional & scientific | 2010 |
| Contract Seating Services Limited | Manufacturing | 1999 |
| Cool Cats Clothing Ltd | Wholesale & retail | 2008 |
| Cooper Brothers (Butterwick) Limited | Agriculture & fishing | 1943 |
| Cooper Road Planing Limited | Construction | 2023 |
| Cope Seeds (UK) Limited | Agriculture & fishing | 2003 |
| Copious Properties Limited | Real estate | 2025 |
| Corbygate Management Limited | Real estate | 1989 |
| Cordatus Security Ltd | Information & communication | 2018 |
| Cordial Canines Limited | Transport & logistics | 2007 |
| Corgi Self Storage Limited | Real estate | 2023 |
| Corptron Ltd | Information & communication | 2025 |
| Corringdon Limited | Real estate | 2016 |
| Cottage Curls Limited | Other services | 2026 |
| Country Chic Boutique Ltd | Manufacturing | 2005 |
| Court ROW Farm Ltd | Other services | 2023 |
| Crampton (Services) Ltd. | Professional & scientific | 2015 |
| Craven Transport Limited | Transport & logistics | 2003 |
| Crawford's Butcher & Baker Ltd | Wholesale & retail | 2025 |
| Crazy B'S Limited | Arts & recreation | 2007 |
| Creaser Family Holdings Limited | Financial services | 2019 |
| Cresta Russell Ltd | Wholesale & retail | 2011 |
| Crewtrident Limited | Education | 2019 |
| Cristiano Brothers Ltd | Hospitality | 2022 |
| Crossways Care Services Ltd | Health & social care | 2022 |
| Crowdog Ltd | Real estate | 2023 |
| Crush Associates Limited | Real estate | 2004 |
| CS Property Services (UK) Ltd | Real estate | 2004 |
| CSC Products Ltd | Manufacturing | 2007 |
| CSM Sameday Ltd | Transport & logistics | 2023 |
| CSS Solutions and Contracting Limited | Professional & scientific | 2014 |
| CT Plastering Ltd | Construction | 2022 |
| Curovia Healthcare Limited | Information & communication | 2024 |
| Curtis Properties (Wrangle) Ltd | Real estate | 2021 |
| Curzon Outsourcing Ltd | Administrative & support | 2025 |
| Custom Computer Programs Limited | Information & communication | 2011 |
| D a Properties (UK) Ltd | Real estate | 2011 |
| D Clark Holdings Ltd | Financial services | 2026 |
| D Hatcher & Sons Limited | Construction | 2009 |
| D Hubbard Accountancy Limited | Professional & scientific | 2013 |
| D. Fisher Renewables Limited | Manufacturing | 2023 |
| D.C. Baxter (Motors) Limited | Wholesale & retail | 1980 |
| D.D. (Grantham) Limited | Real estate | 1989 |
| D.S. Catering Limited | Manufacturing | 2003 |
| Daedalus Integration Ltd | Professional & scientific | 2015 |
| Dafo UK & Ireland Ltd | Construction | 2020 |
| Darren Kime Limited | Transport & logistics | 2022 |
| Darren Sweeney Limited | Extraterritorial | 2014 |
| Datem Ltd | Manufacturing | 2003 |
| Daturu Ltd | Information & communication | 2023 |
| Dave King Carpentry and Building Limited | Construction | 2003 |
| Dave Tebb Ltd | Construction | 2018 |
| David Eager Criminal Defence Ltd | Professional & scientific | 2020 |
| David Fraser Construction Limited | Construction | 2016 |
| David GUY Firewood Merchants Limited | Other services | 2023 |
| Davis Worlds Limited | Other services | 2024 |
| DBY London Limited | Administrative & support | 2019 |
| DC Engineering (Boston) Limited | Manufacturing | 2021 |
| Dctm Biogas Limited | Professional & scientific | 2024 |
| Dctm Contractors Limited | Administrative & support | 2019 |
| Ddam Limited | Real estate | 2024 |
| DDI Consultancy Limited | Information & communication | 2007 |
| DDS Trading Limited | Wholesale & retail | 2014 |
| Deakmont Ltd | Professional & scientific | 2026 |
| Deaks Infrastructure Ltd | Information & communication | 2020 |
| Decarbon Energy Limited | Professional & scientific | 2025 |
| Deckson Holdings Limited | Financial services | 2025 |
| Dees-Gifts Ltd. | Wholesale & retail | 2014 |
| Deli Studio Ltd | Professional & scientific | 2019 |
| Deliciously Grace Limited | Manufacturing | 2021 |
| Deliveries R US Ltd | Transport & logistics | 2025 |
| Destiny Lake Limited | Real estate | 2005 |
| Develop.Ings (Midlands) Ltd | Real estate | 2017 |
| DH Beech Properties Ltd | Real estate | 2021 |
| DHP Developments Ltd | Construction | 2020 |
| Dhsf Properties LLP | | 2023 |
| DHW Financial Services Ltd | Financial services | 2008 |