| Audit Green & Backman Oy Ab | Professional & scientific | 2010 |
| Aura Productions Oy | Information & communication | 2017 |
| Aura, Stenros & Paasonen Oy | Hospitality | 2020 |
| Aurita's Oy | Other services | 2023 |
| Auto Doctor Oy | Other services | 2010 |
| Auto ja Kone Merkkiniemi Oy | Other services | 2018 |
| Auto-Juska Oy | Wholesale & retail | 1993 |
| AutoApp Oy | Wholesale & retail | 2020 |
| AutoWerkz Oy | Wholesale & retail | 2025 |
| Autofix palvelu Oy | Other services | 2024 |
| Autokiri Oy | Wholesale & retail | 1988 |
| Autoleasing Jedi Oy | Wholesale & retail | 2018 |
| Automaali ja -tarvike Sundberg Oy | Wholesale & retail | 1984 |
| Automaatiosuunnittelu J. Nurkkala Oy | Information & communication | 1995 |
| Autopalvelu Kotka Oy | Other services | 2025 |
| Autopesu MOK Oy | Other services | 2020 |
| Autopiste K&M Oy | Other services | 2002 |
| Autotalo Jedi Oy | Wholesale & retail | 2006 |
| Autotalo Järvi Oy | Wholesale & retail | 2000 |
| Autovuokraamo Biilit Oy | Administrative & support | 2025 |
| Avantrum Visuals Oy | Arts & recreation | 2023 |
| Avation Oy | Education | 2022 |
| Avel Ky | Wholesale & retail | 1982 |
| Avenra Oy | Transport & logistics | 2002 |
| Avoin App oy | Information & communication | 2024 |
| Avoin Map Oy | Information & communication | 2020 |
| Avoin Studio Oy | Information & communication | 2024 |
| Avoin yhtiö Iloinen Tulitus | Wholesale & retail | 2010 |
| Avoin yhtiö J & B -kenkä | Wholesale & retail | 1998 |
| Avoin yhtiö L & N Walldén | Wholesale & retail | 1989 |
| Avoin yhtiö Porvoon Auto-Cleaner Borgå Öppet bolag | Other services | 1990 |
| Avoin yhtiö Porvoon MakuAsia, Öppet Bolag Borgå SmakSak | Hospitality | 2001 |
| Avoin yhtiö Topkapi | Hospitality | 1988 |
| B.ardent Oy | Information & communication | 2022 |
| B3 Building Oy | Construction | 2019 |
| BC Grove Oy | Professional & scientific | 2023 |
| BC-Rentservice Ky | Wholesale & retail | 1997 |
| BCM-rakenne Oy/Ab | Construction | 1988 |
| BF Tech Supply Oy | Wholesale & retail | 2024 |
| BG Consulting Oy | Information & communication | 2021 |
| BGM Trading Finland Oy | Wholesale & retail | 2008 |
| Bistro Hopea OY | Hospitality | 2017 |
| BOL Osakeyhtiö | Hospitality | 2014 |
| BPM-Palvelut Oy | Health & social care | 2004 |
| BTF Tilintarkastus Porvoo Oy | Professional & scientific | 2012 |
| BTP Partners Finland Oy | Professional & scientific | 2025 |
| BY Finland Ab | Manufacturing | 2017 |
| Backbone Automation Ab | Information & communication | 2023 |
| Backman Invest Oy | Financial services | 2017 |
| Bagger Oy Ab | Construction | 1989 |
| BailaMas avoin yhtiö | Education | 2018 |
| Balka Oy | Administrative & support | 2023 |
| Baltic Rakennus oy | Construction | 2021 |
| Balticbridge Ab | Transport & logistics | 2026 |
| Barracuda Oy | Hospitality | 2002 |
| Beauty & Body Emotions Ky | Other services | 2007 |
| Before Oy | Wholesale & retail | 1984 |
| Begravningsbyrå Nyman & Co Ab | Other services | 1943 |
| Bennorec Oy | Construction | 1995 |
| Bergholm Fix Oy Ab | Construction | 2018 |
| Besell Oy | Wholesale & retail | 2024 |
| Beside burgers Oy | Hospitality | 2017 |
| Bestgoods, Finland Oy | Construction | 1997 |
| Bewedo Oy | Administrative & support | 2023 |
| Beyond Ordinary Oy | Wholesale & retail | 2025 |
| Bilfinger Finland Oy | Manufacturing | 1986 |
| Bilkim Oy | Wholesale & retail | 2024 |
| Bim Lab Finland Oy | Professional & scientific | 2008 |
| Biodynamite Oy | Wholesale & retail | 2019 |
| Birkitré Oy | Professional & scientific | 2024 |
| Birling Oy | Professional & scientific | 2023 |
| Bistro Mestari Oy | Hospitality | 2025 |
| Black Company Oy | Arts & recreation | 2024 |
| Blomqvist & Blomqvist | Construction | 1983 |
| Blomqvist Audit Oy | Professional & scientific | 2026 |
| Blood Music Oy | Information & communication | 2013 |
| Blu Capita Oy | Real estate | 2019 |
| Blue Gate Oy | Administrative & support | 2011 |
| Blue Safire Oy | Other services | 2020 |
| Blueberry coffee Oy | Hospitality | 2021 |
| Bo Fastigheter Ab | Real estate | 2020 |
| Bodycom Oy | Arts & recreation | 2022 |
| Bofink Capital Oy | Financial services | 2024 |
| Boge Oy | Real estate | 2024 |
| Bohemia Lifestyle Oy | Wholesale & retail | 2017 |
| Bondis Oy | Wholesale & retail | 2022 |
| Bonn Vivre Oy | Professional & scientific | 2023 |
| Bop Oy | Wholesale & retail | 1978 |
| Borgå Lantmanna Ab - Porvoon Maamies Oy | Real estate | 1938 |
| Borgå NSP Bokföringstjänst, öppet bolag | Professional & scientific | 1994 |
| Borgå Plåt Ab - Porvoon Pelti Oy | Construction | 2002 |
| Borgå Plåtarbete Ky Kb | Construction | 1984 |
| Borgå folkakademi Ab | Education | 2005 |
| Bosgård Oy | Agriculture & fishing | 2012 |
| Boss Invest Oy | Real estate | 2019 |
| Bossons Group Oy Ab | Transport & logistics | 2019 |
| Boulder Porvoo Oy | Arts & recreation | 2025 |
| Boule Bistro & Bar Oy | Hospitality | 2021 |
| Boules Oy | Hospitality | 2021 |
| Bowtec Finland Oy | Wholesale & retail | 2020 |