| Dialy Renovation Ltd | Construction | 2019 |
| Diamantem Developments Limited | Construction | 2023 |
| Diamon Valeting Centre Ltd | Wholesale & retail | 2023 |
| Diamond & Daughters Ltd | Real estate | 2024 |
| Diamond Academy Football Club CIC | Education | 2019 |
| Diamond Accountants and General Services Limited | Professional & scientific | 2016 |
| Diamond Auto Services Limited | Wholesale & retail | 2023 |
| Diamond Barber 1 Ltd | Other services | 2025 |
| Diamond Building Works Ltd | Construction | 2021 |
| Diamond Capital Investments Ltd | Financial services | 1997 |
| Diamond Car Limited | Wholesale & retail | 2017 |
| Diamond Care Homes Langdales Ltd | Real estate | 2016 |
| Diamond Care Properties and Investments Ltd | Real estate | 2024 |
| Diamond Care Services Ltd | Real estate | 2022 |
| Diamond Cat 2024 Limited | Hospitality | 2024 |
| Diamond Class Motor Salvage Ltd | Wholesale & retail | 2025 |
| Diamond Class Motors Ltd | Wholesale & retail | 2021 |
| Diamond Clothing Limited | Wholesale & retail | 2017 |
| Diamond Collection Online Ltd | Wholesale & retail | 2024 |
| Diamond Consultants Ltd | Construction | 2010 |
| Diamond Controls Carepay Limited | Professional & scientific | 2021 |
| Diamond Controls Payroll Limited | Professional & scientific | 2018 |
| Diamond Creations Limited | Manufacturing | 1975 |
| Diamond Custom Clearance Ltd | Transport & logistics | 2021 |
| Diamond CUT Barbers Ltd | Other services | 2026 |
| Diamond Dealer Direct Limited | Wholesale & retail | 2006 |
| Diamond Doors Homestay Ltd | Hospitality | 2025 |
| Diamond Drop Draws Ltd | Arts & recreation | 2026 |
| Diamond Edge Property Services Limited | Administrative & support | 2019 |
| Diamond Engagement Rings Limited | Extraterritorial | 2012 |
| Diamond ESC Limited | Administrative & support | 2024 |
| Diamond Facilities Support Limited | Construction | 2010 |
| Diamond Formation Limited | Professional & scientific | 2005 |
| Diamond GA Portfolio Limited | Professional & scientific | 2021 |
| Diamond Glaze 4 U Ltd | Manufacturing | 2024 |
| Diamond Halal Limited | Wholesale & retail | 2024 |
| Diamond Healthcare Ltd | Health & social care | 2006 |
| Diamond Heart Investment Limited | Real estate | 2024 |
| Diamond Hedge Kutters Ltd | Administrative & support | 2026 |
| Diamond Home Support Sandwell Ltd | Administrative & support | 2025 |
| Diamond Homes Building and Maintenance Limited | Construction | 2024 |
| Diamond Housing Ltd | Health & social care | 2013 |
| Diamond Housing Services Ltd | Real estate | 2016 |
| Diamond in the Dirt Ltd | Administrative & support | 2023 |
| Diamond Jewellery Shop Ltd | Wholesale & retail | 2022 |
| Diamond Jules Ltd | Manufacturing | 2018 |
| Diamond Key Living Ltd | Real estate | 2026 |
| Diamond Linen Hire Ltd | Other services | 2011 |
| Diamond Luxury Transfers Limited | Transport & logistics | 2022 |
| Diamond Manufacturers Ltd | Wholesale & retail | 2007 |
| Diamond OFF Licence Limited | Wholesale & retail | 2018 |
| Diamond Personnel Ltd | Manufacturing | 2021 |
| Diamond Properties (Birmingham) Limited | Real estate | 2014 |
| Diamond Properties SSR Limited | Real estate | 2018 |
| Diamond Property Estates Limited | Real estate | 2021 |
| Diamond Property Holdings NE Limited | Real estate | 2022 |
| Diamond Services and Management Ltd | Professional & scientific | 2022 |
| Diamond Shopfront Birmingham Limited | Manufacturing | 2015 |
| Diamond Skills Care & Cleaning Services Limited | Administrative & support | 2025 |
| Diamond Staff Ltd | Information & communication | 2016 |
| Diamond Star Shopping Centre Ltd | Hospitality | 2022 |
| Diamond Stars 2024 Limited | Hospitality | 2024 |
| Diamond Supported Living Ltd | Hospitality | 2025 |
| Diamond Telecommunication Services Limited | Information & communication | 2008 |
| Diamond Tillers Limited | Construction | 2023 |
| Diamond Traders Ltd | Wholesale & retail | 2017 |
| Diamond Travel (Birmingham) Limited | Administrative & support | 2002 |
| Diamond Urban Logistic Limited | Wholesale & retail | 2025 |
| Diamond Urban Storage Limited | Wholesale & retail | 2025 |
| Diamond Vision Ltd | Health & social care | 2022 |
| Diamond Weddings Limited | Other services | 2009 |
| Diamond Yachts Ltd | Manufacturing | 2020 |
| Diamonds Community Learning Project CIC | Education | 2017 |
| Diamonds Events Ltd | Wholesale & retail | 2024 |
| Diamonds Operations Ltd | Administrative & support | 2026 |
| Diamonds Properties Limited | Real estate | 2025 |
| Diamonds Property Ltd | Real estate | 2025 |
| Diamondynasty Limited | Real estate | 2025 |
| Dian Bristol Limited | Hospitality | 2026 |
| Dian Pizza Ltd | Real estate | 2019 |
| Diana Mary Treanor Ltd | Extraterritorial | 2024 |
| Diana Portfolio Ltd | Real estate | 2022 |
| Diane Sathya Jewellery Ltd | Wholesale & retail | 2021 |
| Diane Scott Limited | Wholesale & retail | 2016 |
| Diariolux Ltd | Wholesale & retail | 2023 |
| Diaros Express Ltd | Wholesale & retail | 2024 |
| Diary of the IT MAN Limited | Information & communication | 2018 |
| Diaspora Ltd | Transport & logistics | 2026 |
| Diaspora Together CIC | Agriculture & fishing | 2020 |
| Diaspora Women Arts and Community CIC | Administrative & support | 2025 |
| Diatec Diagnostics Ltd | Professional & scientific | 2003 |
| Diatom Ltd | Transport & logistics | 2024 |
| Diatom Technologies (UK) Ltd | Information & communication | 2026 |
| Dice Film & Animation Ltd | Information & communication | 2016 |
| Dicem Limited | Information & communication | 2025 |
| Diceorama Limited | Manufacturing | 2026 |
| Dickens Heath Road 98-118 RTM Company Limited | Households | 2024 |
| Dickson Services Ltd | Health & social care | 2026 |
| Dicos Transport Ltd | Transport & logistics | 2024 |
| Dida Delivery Ltd | Transport & logistics | 2021 |