| Clement Monreal Resource Limited | Administrative & support | 2022 |
| Clickon Technologies Limited | Information & communication | 2015 |
| Clinical by Ashfield Limited | Education | 2017 |
| Clinicbybae Ltd | Other services | 2026 |
| Clover Healthcare Limited | Health & social care | 2018 |
| CLS Smart Repairs Limited | Wholesale & retail | 2016 |
| CM Mario Recruitment Ltd | Administrative & support | 2025 |
| CM Mario Transport Ltd | Transport & logistics | 2025 |
| CM Quality & Compliance Ltd | Professional & scientific | 2025 |
| CM Records Limited | Information & communication | 2021 |
| CMB Lifting Services Ltd | Construction | 2013 |
| CMM Interiors Ltd | Construction | 2023 |
| CMS North Limited | Professional & scientific | 2023 |
| CMT Training Services Limited | Education | 2021 |
| CMV (Northants) Limited | Transport & logistics | 2012 |
| Cnak Care Services Ltd | Real estate | 2022 |
| CNL Group Ltd | Construction | 2020 |
| Coached by Clough Limited | Education | 2023 |
| Coast Accommodation Ltd | Real estate | 2018 |
| Coastline Property's Ltd | Real estate | 2023 |
| Cobots and Machinery Safety Ltd | Professional & scientific | 2019 |
| Cobra Kebab Ltd | Hospitality | 2024 |
| Cocky Scot Theatre Company Ltd | Professional & scientific | 2015 |
| Codreanu & D Construction Ltd | Construction | 2021 |
| Cofad Ventures Ltd | Wholesale & retail | 2012 |
| Colard Developments Ltd | Real estate | 2002 |
| Collins Petfoods Limited | Wholesale & retail | 2010 |
| Collinsr Holdings Ltd | Professional & scientific | 2018 |
| Colmer Hughes LLP | | 2024 |
| Colombo Spice Ltd | Hospitality | 2024 |
| Colour Dynamics Limited | Wholesale & retail | 2005 |
| Colourscope Flooring and Furniture Ltd | Wholesale & retail | 2024 |
| Comfort Healthcare Ltd | Public administration | 2020 |
| Commerce and Marketing Solutions Ltd | Professional & scientific | 2023 |
| Commtel Innovate Limited | Manufacturing | 2011 |
| Community Rocks | Hospitality | 2007 |
| Compass (Leicester) Limited | Wholesale & retail | 1983 |
| Compass Construction 2025 Ltd | Construction | 2025 |
| Complis Limited | Information & communication | 2005 |
| Compounded Insights Ltd | Professional & scientific | 2025 |
| Comprehensive Business Management Limited | Professional & scientific | 2006 |
| Compro Renewable Energy Ltd | Financial services | 2017 |
| Concept Capital Ltd | Real estate | 2024 |
| Concept Consulting Group Ltd | Education | 2025 |
| Concept Plumbing Contracts Ltd | Construction | 2018 |
| Concerted Care Limited | Health & social care | 2020 |
| Confederation of Construction Specialists Limited | Other services | 2016 |
| Confi Clinic Ltd | Other services | 2023 |
| Conflict Resolution Ltd | Administrative & support | 2025 |
| Connect Motorcycle Parts Limited | Wholesale & retail | 2016 |
| Connect Motorcycle Sales Limited | Wholesale & retail | 2014 |
| Connect Psychology Service Ltd | Education | 2021 |
| CONNECTIONS24HRS Limited | Health & social care | 2016 |
| Connor’S Coaching Consultation Ltd | Arts & recreation | 2024 |
| Constant Companions Limited | Health & social care | 2025 |
| Constant Equity Alpha Limited | Professional & scientific | 2017 |
| Constant Support Service Ltd | Health & social care | 2026 |
| Constant Velocity Joint Limited | Wholesale & retail | 2025 |
| Constantin B Ltd | Transport & logistics | 2025 |
| Construction Leader Ltd | Construction | 2023 |
| Construction Tech Quality Built Ltd | Construction | 2023 |
| Constructiontech Ltd | Construction | 2025 |
| Consultants 24 Limited | Professional & scientific | 2024 |
| Contact Point Security Ltd | Administrative & support | 2022 |
| Conti Group Ltd | Transport & logistics | 2017 |
| Conti Logistic Ltd | Transport & logistics | 2018 |
| Continuance Capital Ltd | Professional & scientific | 2020 |
| Continuance Capital Partners Limited | Professional & scientific | 2025 |
| Cool Duck Ltd | Wholesale & retail | 2020 |
| Cool Logistics 17 Ltd | Transport & logistics | 2023 |
| Cool Move Mario Limited | Transport & logistics | 2008 |
| Coolbox Solutions Limited | Administrative & support | 2021 |
| Coolpack Solutions Limited | Administrative & support | 2026 |
| Corazon FP Limited | Other services | 2020 |
| Corbie Window Blinds Ltd | Manufacturing | 2024 |
| Corby Indian Cuisine Ltd | Hospitality | 2026 |
| Corby & District Cancer Care | Health & social care | 1997 |
| Corby & District Cancer Care Trading Limited | Administrative & support | 2008 |
| Corby Accounts & Payroll Services Ltd | Professional & scientific | 2016 |
| Corby Athletic Club CIC | Arts & recreation | 2013 |
| Corby Auto Cars Ltd | Wholesale & retail | 2024 |
| Corby Automation Maintenance Services Limited | Professional & scientific | 2025 |
| Corby Blinds Ltd Ltd | Manufacturing | 2025 |
| Corby C.T.C Trading Limited | Arts & recreation | 1995 |
| Corby CAN Community Interest Company | Arts & recreation | 2022 |
| Corby Car Clinic Limited | Manufacturing | 2018 |
| Corby Care Group Ltd | Professional & scientific | 2026 |
| Corby Children's Centre Consortium C.I.C. | Professional & scientific | 2016 |
| Corby Cleaning Fairies Limited | Administrative & support | 2022 |
| Corby COD Ltd | Administrative & support | 2015 |
| Corby Coffee Roasting Company Ltd | Manufacturing | 2017 |
| Corby Commercials Limited | Wholesale & retail | 2021 |
| Corby Commissioning Services Limited | Professional & scientific | 2024 |
| Corby Community Arts Association Limited | Education | 1979 |
| Corby Community Energy Limited | Other services | 2016 |
| Corby Community Property Development Ltd | Construction | 2025 |
| Corby Computer Clinic Limited | Other services | 2010 |
| Corby Covers Ltd | Manufacturing | 2017 |
| Corby Custom Carpentry Ltd | Construction | 2018 |
| Corby Cutz Ltd | Other services | 2026 |