| Ardmillan Mill Pond Ltd | Ballyclare | 2012 |
| Ardmore Developments Limited | Co.Down | 1989 |
| Ardmore Management Limited | Bangor | 1991 |
| Ardmore Trustee Services Ltd | Carluke | 2010 |
| Ardnagreena House Property Management Limited | Belfast | 2003 |
| Ardonagh Corporate Secretary Limited | London | 1999 |
| Ardora Health Ltd | London | 2024 |
| Ardovries UK Limited | Ashford | 1991 |
| Ardowen Ltd | Crumlin | 2023 |
| Ardrossan Storage Company Limited | Prestwick | 2022 |
| Ardrox Limited | Milton Keynes | 1948 |
| Ards Building Products (Manufacturing) Limited | Belfast | 1990 |
| Ards Trust Limited | Dromore | 1999 |
| Ardsley 1956 Limited | Barnsley | 2013 |
| Ardudwy Distillery Ltd | Telford | 2015 |
| Ardudwy Management Company Limited | Aberdovey | 1987 |
| Ardverna Energy Limited | Ballymena | 1985 |
| Ardvinister Limited | Newbridge | 2021 |
| Ardwick Developments Limited | Liverpool | 2016 |
| ARE Purchasing Solutions Ltd | Swansea | 2018 |
| ARE YOU Safe GAS Ltd | Hoddesdon | 2017 |
| Area 51 Cars Limited | Stoke On Trent | 2021 |
| Area 51 Investments Limited | Stoke On Trent | 2021 |
| Area 51 Yacht Limited | London | 2019 |
| Area Energy OIL & GAS Ltd. | London | 2015 |
| Area Fifty One Limited | Harrogate | 2012 |
| Area Limited | Guildford | 2000 |
| Arealhus Innlandet Invest Limited | London | 2020 |
| Areaview (Southern) Limited | Surrey | 2004 |
| Arecom Limited | London | 2019 |
| Areen Design Services Limited | London | 2018 |
| Arel Ocean Ltd | London | 2024 |
| Arel Services Limited | Road, Dudley | 1965 |
| Areley Healthcare Limited | Walsall | 2025 |
| Arema Farms Limited | Hitchin | 1978 |
| Aremi Limited | Bourne | 2000 |
| Aren Trading Limited | Bury | 2021 |
| Aren Yachting Ltd | Blackpool | 2024 |
| Arena Business Centres Basingstoke Limited | Southampton | 2020 |
| Arena Island Limited | London | 2015 |
| Arenafleet Limited | Norwich | 2002 |
| Areno Limited | Manchester | 2021 |
| Arenza Ventures Ltd | London | 2025 |
| Areon Investments Limited | Manchester | 2021 |
| Ares Boating Limited | London | 2024 |
| Ares International Co. Limited | London | 2006 |
| Ares Trade Co., Ltd | Cambridge | 2013 |
| Ares Waves Ltd | London | 2025 |
| Ares Yachting Ltd | Bromley | 2024 |
| Aresais International Holding Group Limited | Beckenham | 2019 |
| Arete Asia Research Limited | London | 2007 |
| Arete Homelets Limited | Hove | 2011 |
| Arete Prints Limited | Shaftesbury | 2024 |
| Areto Homes Limited | Hartlepool | 2020 |
| Areus Limited | Harrogate | 2009 |
| Areva Bodywork Limited | Swadlincote | 1979 |
| Areva Services Limited | Swadlincote | 1990 |
| Arewen Limited | Newport | 2003 |
| Arfa Treasure Ltd | Chepstow | 2021 |
| Arfligton Limited | London | 2024 |
| ARG Pensions (1974) Limited | Leamington Spa | 1954 |
| ARG Trustees (1970) Limited | Leamington Spa | 1968 |
| Argania Naturale Ltd | Guildford | 2013 |
| Argent By-Products Group Limited | Colchester | 1932 |
| Argent Europe Limited | Colchester | 1996 |
| Argent Foods Group Limited | Colchester | 2016 |
| Argenta River Ltd | Ruislip, | 2023 |
| Argentum Law (UK) Ltd | London | 2019 |
| Argima Ltd | Dover | 2007 |
| Argo Mediterranean Holdings Ltd | Woodbridge | 2023 |
| Argoed Quarry Ltd | Pontyclun | 2009 |
| Argon (NES 1) Limited | Newcastle Upon Tyne | 2024 |
| Argon Health (Seaton Delaval) Ltd | Newcastle Upon Tyne | 2024 |
| Argonaut 2020 Limited | Tonbridge | 2017 |
| Argot Properties Limited | Birmingham | 1988 |
| Argus Analytics Limited | London | 2021 |
| Argus Investment Sweden Limited | London | 2021 |
| Argus Media Africa Limited | London | 2020 |
| Argus Security Systems Limited | Manchester | 2014 |
| Argyll Aquaculture Ltd | Oban | 2022 |
| Argyll Motor Company Limited | London | 2015 |
| Argyll Valet Center Limited | Dunoon | 2022 |
| Argyll-Brent Contracts Ltd | High Wycombe | 2006 |
| ARH Athletics Equipment Ltd | Haverhill | 2015 |
| ARI Building Materials Co., Ltd | Beckenham | 2024 |
| Aria Court 1963 Limited | Derby | 2014 |
| Aria DD Ltd | Maidenhead | 2024 |
| Aria Global Group Ltd | London | 2018 |
| Aria Homes Limited | York | 1988 |
| Aria Rose Revell Ltd | Droitwich | 2025 |
| Ariah Services Limited | Southport | 2010 |
| Arian Investments Limited | Cobham | 2015 |
| Ariana Global Limited | Loughton | 2005 |
| Ariandy Limited | Caernarfon | 2013 |
| Ariane Investments Limited | London | 2007 |
| Aricanli Ltd | London | 2025 |
| Arics Limited | Banbury | 2000 |
| Aridis Marine Limited | London | 2025 |
| Arif Gardner Limited | St Albans | 2010 |
| Arigatou Ltd | Sutton | 2023 |