| B-Line Homes Ltd | Real estate | 2016 |
| B.A.Ribs Limited | Manufacturing | 2016 |
| B.G. Automotive Limited | Wholesale & retail | 1998 |
| B.J.S. GAS Appliance Centre, Heating & Plumbing Limited | Construction | 2004 |
| B.K.I Services Ltd | Construction | 2022 |
| B.Mannings Services Limited | Administrative & support | 2025 |
| B1 Property Developments Ltd | Construction | 2026 |
| B4 Actio Ltd | Professional & scientific | 2023 |
| B4 Construction (South) Ltd | Construction | 2013 |
| B4 Construction (SW) Ltd | Construction | 2024 |
| B4 Construction (Wiltshire) Ltd | Construction | 2024 |
| B4 Construction Group Ltd | Construction | 2026 |
| B4 Construction Limited | Construction | 2008 |
| Bab's Barbershop Ltd | Other services | 2026 |
| Baboon Adventures Ltd | Administrative & support | 2021 |
| Baby Boppers Ltd | Arts & recreation | 2009 |
| Baby Swimmers LLP | | 2012 |
| Babyspoon Limited | Information & communication | 2023 |
| Back in the Day Media Ltd | Wholesale & retail | 2026 |
| Backwell Dental Care Limited | Health & social care | 2010 |
| Backyard Cabins Limited | Other services | 2020 |
| Baco Trans Ltd | Transport & logistics | 2016 |
| BAD Blood Films Limited | Information & communication | 2013 |
| Badbury Orchard Management Company Limited | Households | 2026 |
| Badbury Property Developments Ltd | Construction | 2022 |
| Badbury Services Limited | Education | 2012 |
| BADEX02 Ltd | Health & social care | 2015 |
| Badger Bases Limited | Other services | 2023 |
| Badger Consulting (UK) Limited | Professional & scientific | 2026 |
| Badingham Limited | Professional & scientific | 2009 |
| Bae-Mac Surfacing Ltd | Construction | 2025 |
| Bagbury Homes Ltd | Construction | 2008 |
| Baguley Estates Limited | Real estate | 2025 |
| Bahati Limited | Information & communication | 2000 |
| Baika Beauty Ltd | Wholesale & retail | 2017 |
| Baila C&V Limited | Hospitality | 2014 |
| Bailera Ltd | Transport & logistics | 2022 |
| Bailey Adams Limited | Professional & scientific | 2016 |
| Bailey Escapes Ltd | Administrative & support | 2025 |
| Bailey Fasteners Limited | Manufacturing | 2019 |
| Baileys Vehicle Services Ltd | Wholesale & retail | 2022 |
| Baize & Wool Ltd | Wholesale & retail | 2018 |
| Baker & Sons Construction Limited | Construction | 2022 |
| Baker Family Capital Limited | Financial services | 2026 |
| Baker Roofing Swindon Limited | Construction | 2020 |
| Baker Rose Wealth Ltd | Professional & scientific | 2026 |
| Bakers & Sons Scaffolding Ltd | Construction | 2019 |
| Bakers Scaffolding Limited | Construction | 2006 |
| Balance Accountancy Ltd | Professional & scientific | 2020 |
| Balancing Dynamics Ltd | Administrative & support | 2009 |
| Baldwin Brothers (Builders) Limited | Construction | 1958 |
| Balgay Ltd | Wholesale & retail | 2024 |
| Baliyans Limited | Professional & scientific | 2023 |
| Balkan Export UK Ltd | Wholesale & retail | 2024 |
| Ballantyne Supercar Services Limited | Wholesale & retail | 2024 |
| Ballard Building Services Limited | Construction | 2025 |
| Ballast Tools (UK) Limited | Manufacturing | 1990 |
| Ballivar Limited | Professional & scientific | 2005 |
| Balmoral Park (Swindon) Management Company Limited | Households | 2008 |
| Baltic Supermarket Swindon Ltd | Wholesale & retail | 2025 |
| BAM Property Portfolio Ltd | Real estate | 2025 |
| BAM Smarts Limited | Information & communication | 2026 |
| Bana BA Sawa UK | Health & social care | 2021 |
| Bancumm Surfacing Limited | Construction | 2004 |
| Bandeira Consulting Services Ltd | Professional & scientific | 2022 |
| Bandel Limited | Health & social care | 2015 |
| Bandesha Group Ltd | Transport & logistics | 2025 |
| Bandido Events UNO Ltd | Hospitality | 2025 |
| Bandidos DOS Limited | Hospitality | 2023 |
| Bangel Dinning Ltd | Hospitality | 2016 |
| Bangla Bazaar Swindon Ltd | Wholesale & retail | 2024 |
| BAO K Limited | Health & social care | 2022 |
| Baqaa UK Ltd | Information & communication | 2025 |
| Bar Grip Tyres Limited | Wholesale & retail | 2023 |
| Bar Structuring UK Ltd | Wholesale & retail | 2020 |
| BAR32 Ltd | Hospitality | 2022 |
| Barber Blade Westbury Ltd | Other services | 2025 |
| Barber Zone 1 Ltd | Other services | 2023 |
| Barbrook Management Company Ltd | Financial services | 2012 |
| Barbury Castle Ltd | Wholesale & retail | 2018 |
| Barbury Retail Ltd | Wholesale & retail | 2020 |
| Barbury Safety Limited | Construction | 2016 |
| Barbury Shooting School Limited | Arts & recreation | 2019 |
| Barchem Pools Ltd | Construction | 1977 |
| Barclay Residential Limited | Real estate | 2026 |
| Bare Consultancy Ltd | Professional & scientific | 2025 |
| Bare Glazed Pottery Studio Ltd | Arts & recreation | 2026 |
| Barileon Limited | Other services | 2013 |
| Baristocats Ltd | Hospitality | 2015 |
| Baristocats Swindon Ltd | Hospitality | 2026 |
| Barnabas AID Limited | Health & social care | 2000 |
| Barnard Laboratories Limited | Health & social care | 2014 |
| Barnes Yard Management Company Limited | Extraterritorial | 2012 |
| Barnes,Branch & Co.Limited | Manufacturing | 1929 |
| Barnesfield Timber Ltd | Wholesale & retail | 2015 |
| Barnets Barber 1 Ltd | Other services | 2018 |
| Barnswood Holdings Ltd | Real estate | 2022 |
| Barnum Court Freehold Ltd | Households | 2018 |
| Baroni Assets Limited | Real estate | 2023 |
| Baroni Projects Limited | Real estate | 2025 |