| Advent Financial Services Limited | Harrow | 2021 |
| Advent Global Opportunities Management Ltd | London | 2016 |
| Advent Group Capital Limited | London | 2024 |
| Advent Insurance Services Limited | Cheltenham | 1998 |
| Advent International Ltd | London | 1989 |
| Advent Ltd | Bury St. Edmunds | 2024 |
| Advent Management Life Sciences Limited | Edinburgh | 2009 |
| Advent Solutions Holdings Limited | London | 2003 |
| Advent Solutions Management Limited | London | 2000 |
| Advent Underwriting Limited | Brighton | 1975 |
| Advent Wealth Limited | London | 2018 |
| Adventure & Expedition Ltd | Caergeiliog | 2019 |
| Adventure FG Ltd | London | 2025 |
| Adventure Golf Holdings Ltd | Windsor | 2017 |
| Adventure Holdings Limited | Old Felixstowe | 2019 |
| Adventure Network Holdings Limited | Epsom | 2018 |
| Adventure Peaks Property Holdings Limited | Ambleside | 2018 |
| Adventure Toys Holdings Ltd | Northallerton | 2024 |
| Adventures in Compassionate Commerce | Hornchurch | 2017 |
| Adventures in Time + Space Ltd | Moon Lane | 2019 |
| Adventures Partners UK I Ltd | London | 2020 |
| Adventures Partners UK II Energy Ltd | London | 2020 |
| Adventurous FOX Limited | Taunton | 2016 |
| Adventurous Holdings Limited | Saffron Walden | 2024 |
| Adventus Innovation Limited | Bedford | 2018 |
| Adventus Nominees Limited | Cardiff | 2024 |
| Adventus Partners Limited | Bedford | 2018 |
| Adverge Limited | Weymouth | 2021 |
| Adverse Money Limited | Darlington | 2019 |
| Adversio Group Limited | Reading | 2024 |
| Advertytics Ltd | Egham | 2021 |
| Advg Holdings Limited | Manchester | 2023 |
| Advias Ltd | Hitchin | 2021 |
| Advice 1ST Limited | Harpenden | 2023 |
| Advice 4U Financial Planning Ltd | Tewkesbury | 2015 |
| Advice and Solutions Limited | Co. Durham | 2004 |
| Advice Centre Group Ltd | Cheadle | 2022 |
| Advice Champion Services Limited | Leeds | 2019 |
| Advice Champion.Co.Uk Limited | Leeds | 2011 |
| Advice Ecosystem Technologies Limited | London | 2024 |
| Advice First Limited | London | 2001 |
| Advice for Later Life Ltd | Chichester | 2019 |
| Advice for Life Holdings Limited | Dumfries | 2021 |
| Advice for Life Ltd | Chichester | 2024 |
| Advice Holdings Limited | Marlow | 2022 |
| Advice Made Simple Limited | Guildford | 2006 |
| Advice Matters Financial Planning Ltd | Otley | 2017 |
| Advice on Pensions Limited | Harrow | 2008 |
| Advice Point Group Ltd. | Harrow | 2016 |
| Advice Solutions Limited | Chatham | 2021 |
| Advice Ventures Ltd | London | 2020 |
| Advice Wise Ltd | Sutton Coldfield | 2018 |
| Advice YOU CAN Trust Limited | Rotherham | 2024 |
| ADVICE2U Ltd | Tunbridge Wells | 2022 |
| Adviceon... Ltd | Stroud | 1986 |
| Advicorp Public Limited Company | Harrow | 1997 |
| Advictus Ltd | London | 2024 |
| Advies Wealth Management Ltd | Diss | 2013 |
| Advin SPV1 Limited | York | 2024 |
| Advisability Limited | London | 2015 |
| Advisant Capital Advisors Limited | London | 2024 |
| Adviscen Ltd | London | 2023 |
| Advise Able Ltd | Chatham | 2017 |
| Advise and Protect Limited | Bristol | 2012 |
| Advise My Mortgage & Protection Ltd | Dunfermline | 2025 |
| Advise YOU Ltd | Slough | 2023 |
| Advised Financial Limited | Farnborough | 2014 |
| Adviser Business Solutions Limited | Emsworth | 1999 |
| Adviser Circle Limited | Chatham | 2025 |
| Adviser Services Group Holdings Limited | Knutsford | 2024 |
| Adviser Services Holdings Limited | Knutsford | 2019 |
| Adviser Solutions Ltd | Abergele | 2014 |
| Adviser Technologies Limited | London | 2017 |
| Adviserhome Limited | York | 2011 |
| Adviserplus Holdings Limited | Ellesmere Port | 2014 |
| Advisertech Connect Limited | Stockport | 2026 |
| Advisertime Limited | Rickmansworth | 2008 |
| Advising Mortgages 4 U Ltd | Peterborogh | 2018 |
| Advismart Ltd | London | 2025 |
| Advisor Hub Limited | Rochester | 2025 |
| Advisor Trusts and Probate Services Ltd | Hertford | 2007 |
| Advisory Broking Ltd | Wimborne | 2023 |
| Advisory II Ltd | London | 2026 |
| Advisory Insurance Brokers Limited | London | 2000 |
| Advisorylondon Networks Limited | London | 2016 |
| Advisum Limited | London | 2026 |
| Advitam Wellness Ltd | London | 2022 |
| Advnsys UK Holding Limited | Holywell | 2025 |
| Advocate Finance Limited | Essex | 2005 |
| Advocate Financial Planning Ltd | St. Asaph | 2014 |
| Advocate Mortgage & Protection Ltd | Huntingdon | 2025 |
| Advocates Pharma Holdings Limited | Workington | 2013 |
| Advsr Holdco Ltd | London | 2022 |
| ADW Financial Limited | Newcastle Upon Tyne | 2025 |
| ADW Financial Solutions Limited | Ruislip | 2017 |
| ADW Holdings (Scotland) Limited | Glasgow | 2022 |
| ADW Holdings Ltd | Bradford | 2009 |
| Adwa International Holdings Ltd | Derby | 2020 |
| Adwanted UK Limited | London | 2020 |
| Adwc Ltd | Harrow | 2025 |