| Interweb Builder Limited | Professional & scientific | 2012 |
| IOS Land Ltd | Administrative & support | 2023 |
| Iwjt | Financial services | 2017 |
| J Butterfield General Dealer Ltd | Agriculture & fishing | 2025 |
| J W Bainbridge Contractors Ltd | Administrative & support | 2010 |
| J&G Consulting Services Limited | Administrative & support | 2018 |
| J.E.D Building Contractors Limited | Construction | 2023 |
| James Lambert Architects Limited | Professional & scientific | 2008 |
| Jane Ascroft Accountancy Limited | Professional & scientific | 2007 |
| Jasmin Management Services Limited | Hospitality | 2025 |
| JAY CEE Transport Limited | Transport & logistics | 2002 |
| Jennie Stafford Rural Advisory Ltd | Agriculture & fishing | 2011 |
| Jenscape Limited | Construction | 2015 |
| JGR Operators Limited | Construction | 2013 |
| JK Cleaning (Co. Durham & Yorkshire) Ltd | Administrative & support | 2019 |
| JK Cleaning (Durham & Tees Valley) Ltd | Administrative & support | 2024 |
| JK Waste Management Services Ltd | Water & waste | 2025 |
| JMG Builders (Northern) Limited | Construction | 2013 |
| JO Saint Marketing Ltd | Professional & scientific | 2018 |
| John Dobson Plant Hire Limited | Construction | 2003 |
| Jonathan Wallis CS Limited | Professional & scientific | 2021 |
| Joplings Tree Services Ltd | Agriculture & fishing | 2022 |
| JP Damp Proofing Ltd | Construction | 2025 |
| JR. Plant Maintenance Limited | Manufacturing | 2016 |
| JRL UK Commercials Limited | Wholesale & retail | 2016 |
| JRV Engineering Management Services Limited | Professional & scientific | 2016 |
| Jtpcs Limited | Professional & scientific | 2016 |
| Juliette Lowe Health & Safety Services Ltd | Professional & scientific | 2023 |
| Just AGL Limited | Professional & scientific | 2018 |
| K. D. Peart Ltd. | Manufacturing | 2012 |
| Kane Conway Ltd | Administrative & support | 2025 |
| KAT Farm Services Limited | Agriculture & fishing | 2019 |
| KCS North Limited | Professional & scientific | 1991 |
| Kearton Crushing & Screening Holdings Limited | Extraterritorial | 2025 |
| Kearton Farms Limited | Construction | 2009 |
| Kelsall Consulting Limited | Professional & scientific | 2015 |
| KEN Proud Consultancy & Contracting Ltd | Professional & scientific | 2023 |
| Kiveal QP and Auditing Limited | Professional & scientific | 2021 |
| Klostel Ventures Limited | Professional & scientific | 2023 |
| KMS Consultancy(Uk) Ltd | Professional & scientific | 2026 |
| KMS Roofing Limited | Construction | 2003 |
| Kneller Plumbing and Heating Limited | Construction | 2023 |
| Kreemys Ltd | Financial services | 2019 |
| Kyani Limited | Information & communication | 1998 |
| Kysu Limited | Professional & scientific | 2022 |
| Labour of Wood Ltd | Manufacturing | 2015 |
| Landquip U.K. Ltd | Wholesale & retail | 2023 |
| Lartington Lakes Ltd | Agriculture & fishing | 2025 |
| Lawthotics Ltd | Administrative & support | 2023 |
| Lcnr Solutions Limited | Information & communication | 2025 |
| LD Sales & Marketing Ltd | Professional & scientific | 2020 |
| Lee-Shield Builders Limited | Construction | 2003 |
| LEO Applegarth Electrical Contractors Limited | Construction | 2014 |
| Lewis Family Property Holdings Co Ltd | Hospitality | 2016 |
| LFP Ben-Nevis Limited | Hospitality | 2017 |
| LFP Highland Limited | Hospitality | 2017 |
| LFP Jacobite Limited | Hospitality | 2017 |
| Life Kitchen Social Community Interest Company | Health & social care | 2018 |
| Life Publishing Group Ltd | Manufacturing | 2026 |
| Little Dog Properties Limited | Real estate | 2025 |
| Live in Motion Ltd | Manufacturing | 2020 |
| Lloyton Commercial & Rail Ltd | Professional & scientific | 2015 |
| Lonton Coffee Company Ltd | Manufacturing | 2013 |
| Lonton Leisure Ltd | Hospitality | 2023 |
| Lord Eden Holdings Limited | Professional & scientific | 2019 |
| Louis Smith Motors Limited | Real estate | 1959 |
| LOW Mill Management Company Limited | Households | 1991 |
| Lowson Street MOT Centre Ltd | Wholesale & retail | 2016 |
| Lucy Charlesworth Consulting Ltd | Professional & scientific | 2025 |
| Luke Bannister Plumbing & Heating Ltd | Construction | 2018 |
| Luke Maskell Limited | Professional & scientific | 2022 |
| Lunehead Properties Ltd | Real estate | 2024 |
| M & C Cards Limited | Wholesale & retail | 2018 |
| M F & K C Stobart Limited | Agriculture & fishing | 2006 |
| M J Close & SON Ltd | Transport & logistics | 2008 |
| Macs (NE) Ltd. | Professional & scientific | 2011 |
| Maddox & Maddox Limited | Professional & scientific | 2019 |
| Made in Deerbolt C.I.C. | Wholesale & retail | 2025 |
| Magik 4 Kids | Education | 2006 |
| Malcolm Riley Associates Limited | Professional & scientific | 2002 |
| Mangolia Ltd | Wholesale & retail | 2020 |
| Manor Court Services Limited | Other services | 2000 |
| Mantra Business Solutions Ltd | Professional & scientific | 2025 |
| Marine Engineering & Sailing Tuition Services Ltd | Professional & scientific | 2014 |
| Mark Gibson Motor Services Limited | Wholesale & retail | 2011 |
| Mark Hardcastle Limited | Wholesale & retail | 2019 |
| Mark Winter Electrical Limited | Construction | 2007 |
| Marlowe Metal Trading Ltd | Wholesale & retail | 2022 |
| Martin Greaves Limited | Manufacturing | 2023 |
| Marwood Caravan Park Limited | Hospitality | 2008 |
| Mcart Studios Ltd | Arts & recreation | 2012 |
| Mcgarry Law (Dales) Limited | Professional & scientific | 2022 |
| Mcgarry Law LLP | | 2021 |
| Mcnabs Books Ltd | Wholesale & retail | 2018 |
| Mcrocklin Ltd | Information & communication | 2021 |
| Medical English UK LLP | | 2025 |
| Medley Automotive Ltd | Wholesale & retail | 2026 |
| Melvir Associates Ltd | Construction | 2007 |
| MGC Management Services Limited | Professional & scientific | 2024 |
| Mickleton Engineering Limited | Wholesale & retail | 2002 |