| Audioprint Ltd | Bedford | 1985 |
| Audioscenic Limited | Southampton | 2017 |
| Audioserv Limited | Pudsey | 2004 |
| Audioset Ltd | Stevenage | 2011 |
| Audiosigns Ltd | Richmond | 2015 |
| Audiostore Ltd | Tunbridge Wells | 2017 |
| Audioville Ltd | London | 2020 |
| Audiovox Publishing Ltd | Grimsby | 2025 |
| Audis Electrical Services Ltd | Kettering | 2010 |
| Audit Diagnostics (N.I.) Ltd | Antrim | 2016 |
| AUDIT365 Limited | London | 2024 |
| Auditel Rental and Service Limited | High Wycombe | 2008 |
| Auditel Systems Integration Limited | High Wycombe | 2011 |
| Auditel Systems Limited | High Wycombe | 2018 |
| Auditoria Services Limited | Rotherham | 1977 |
| Auditorium Perfumes Ltd | Mildenhall | 2026 |
| Audiverse CIC | Newcastle Upon Tyne | 2025 |
| Audley Scientific Limited | Middlesex | 1986 |
| Audmented Reality Limited | London | 2018 |
| Audo Player Ltd | London | 2025 |
| Audrey Alexander Fashion Ltd | Harrow | 2018 |
| Audrey Johns Limited | Pembrokeshire | 2005 |
| Audrey London Atelier Ltd | Bexleyheath | 2022 |
| Audrys Painting and Decorating Ltd | Hornchurch | 2026 |
| Audus Noble Plastics Limited | Humshaugh | 1964 |
| Audyssey Ltd | Penrith | 2023 |
| AUE Natural Limited | London | 2024 |
| Aufguss Saunas Ltd | Selby | 2025 |
| AUG Composites Limited | Bridgwater | 2016 |
| AUG Rose Club Ltd | London | 2025 |
| Aug-Corp Limited | Wetherby | 2024 |
| Auger Torque Europe Limited | Cheltenham | 1998 |
| Auggus Ltd | London | 2016 |
| Aughton Engineering Services Limited | Llandudno Junction | 2017 |
| Aughton F Limited | Preston | 2020 |
| Augma Biomaterials UK Limited | London | 2024 |
| Augmented Instruments Ltd | London | 2016 |
| Augmentory.Com Limited | Wakefield | 2015 |
| Augr Limited | London | 2019 |
| Augus Engineering Limited | West Bromwich | 1997 |
| August Bakery Ltd | Richmond | 2024 |
| August Bicycles Ltd | Norwich | 2015 |
| August Hill Ltd | London | 2025 |
| August Race EU Ltd | Belfast | 2026 |
| Augusta Boat Services Limited | Nottingham | 2026 |
| Augusta Life Sciences UK Limited | Wokingham | 2025 |
| Augusta Plumbing Ltd | Abertillery | 2012 |
| Augustina's Love Ltd | Edgware | 2023 |
| Augustus Martin Limited | Bromley-By-Bow | 1969 |
| Augustus Oils Limited | Alton | 1985 |
| AUK Distribution Ltd | Cramlington | 2009 |
| AUK Ltd | Burntwood | 2025 |
| AUK Realisations Limited | 1 Oxford St | 1971 |
| Aukitchen Limited | Hollinwood | 2019 |
| AUKP1 Ltd | Nether Alderley | 2022 |
| AUKP2 Ltd | Nether Alderley | 2022 |
| Aukselis Ltd | London | 2020 |
| Auld Bond Bottlers Ltd | Perth | 2020 |
| Auld Friend Limited | Somerton | 2018 |
| Aulds Bakeries Limited | Renfrewshire | 1999 |
| Aulds Delicious Desserts Limited | Renfrewshire | 1967 |
| Aulds Holdings Limited | Renfrewshire | 1999 |
| Aulds Retail Limited | Greenock | 2018 |
| Aulds the Bakers Ltd | Greenock | 2013 |
| Auli London Ltd | London | 2016 |
| Ault Ltd | London | 2026 |
| Aultkilts Ltd | Glasgow | 2025 |
| Aulton & Butler Limited | Walsall | 1955 |
| Aulumbee Limited | Ipswich | 2020 |
| AUM Apparel Ltd | Canterbury | 2025 |
| AUM Clothing Ltd | London | 2020 |
| AUM Incorporated Limited | Hitchin | 2021 |
| AUM Kitchen Ltd | Wembley | 2021 |
| AUM LAB Ltd | Chester | 2026 |
| Aumari Living Ltd | London | 2025 |
| Aumecon Limited | Mansfield | 2006 |
| Aumnik Ltd | Northwood | 2018 |
| Aumovio Engineering Solutions Limited | Lichfield | 1995 |
| Aumovio Systems UK Limited | Blaenau | 1961 |
| Aumovio Trading UK Limited | West Midlands | 1969 |
| Aumovio UK Limited | Birmingham | 1970 |
| Aunate Ltd | Huddersfield | 2024 |
| Aune Valley Meat Limited | Ivybridge | 2010 |
| Aunger Guitars Ltd | Houghton Le Spring | 2017 |
| Aunstech Limited | Sheffield | 2024 |
| Aunt Gee's Ltd. | London | 2012 |
| Aunt Polly's Ltd | Cleator Moor | 2025 |
| Aunt Sally's Ltd | Wolverhampton | 2009 |
| Auntie Cazzie's Kitchen Ltd | Beverley | 2026 |
| Auntie Shade's Ltd | London | 2023 |
| Auntie's Sauces Ltd. | Coventry | 2018 |
| Auntiepenny's Ltd | Southampton | 2023 |
| Aunty Almas Ltd | Leigh | 2019 |
| Aunty Fifi's Kitchen Ltd | London | 2020 |
| Aunty RAG Ltd | Chester | 2011 |
| Aunty Ree's Cookies and More Ltd | Sudbury | 2025 |
| Aunty Sybil's Ltd | Stockport | 2024 |
| AUR Cymru Limited | Scarborough | 2013 |
| Aura & Amber Candle Co Ltd | London | 2025 |
| Aura Aerospace Ltd | Morpeth | 2025 |