| Parkhouse Winchmore Hill Limited | Real estate | 2003 |
| Parking Options Ltd | Professional & scientific | 2022 |
| Parkside Gardens (Watford) Residents Limited | Households | 2012 |
| Parkside Recruitment Limited | Administrative & support | 1982 |
| Parkside Recruitment Services Limited | Administrative & support | 2006 |
| Parkview Residents Association Limited | Households | 1970 |
| Parkwood Property Investments Ltd | Real estate | 2023 |
| Parm Dhillon Limited | Information & communication | 2007 |
| Parmar Homes Ltd | Real estate | 2020 |
| Parmar Refinery Ltd | Water & waste | 2015 |
| Parmiter's School | Education | 2011 |
| Parratt Plumbing & Heating Ltd | Construction | 2019 |
| Parry Media Services Ltd | Information & communication | 2014 |
| Parrys Amersham Limited | Construction | 2005 |
| Part Exchange Homes Limited | Real estate | 2010 |
| Partas Global Limited | Professional & scientific | 2019 |
| Partner DE Novo Ltd | Professional & scientific | 2012 |
| Partridge ST George Ltd | Hospitality | 2024 |
| Party DEY Here Limited | Hospitality | 2024 |
| Parus Capital Services Limited | Financial services | 2016 |
| Parvathi Nair Consulting Limited | Professional & scientific | 2019 |
| Paska Limited | Hospitality | 2006 |
| Paska Properties Limited | Hospitality | 2016 |
| Passaic Investments Limited | Administrative & support | 2019 |
| Passaic Services Limited | Financial services | 2017 |
| Passion Healthcare Watford Ltd | Administrative & support | 2022 |
| Passmasters Motorcycle Training Ltd | Education | 2024 |
| Pastael Limited | Wholesale & retail | 2024 |
| Patadia Limited | Information & communication | 2022 |
| Patel Consultant Limited | Professional & scientific | 2015 |
| Patel Thakor Estates Ltd | Real estate | 2026 |
| Pathfinder GTM Limited | Information & communication | 2009 |
| Pathfinder K9 Security Ltd | Administrative & support | 2025 |
| Pathfinders Care Services Limited | Health & social care | 2018 |
| Pathmakers Marketing Ltd | Professional & scientific | 2011 |
| Patient Choice International Ltd | Health & social care | 2015 |
| Patient Protect Ltd | Professional & scientific | 2025 |
| Patrick Gill Consultants Limited | Administrative & support | 2000 |
| Patrick Scott Loss Adjusting Ltd | Financial services | 2019 |
| Patronat Co. Ltd | Manufacturing | 2023 |
| Patronus Properties Limited | Real estate | 2013 |
| Patronus Services Ltd | Real estate | 2023 |
| Pattronus Limited | Real estate | 2015 |
| Patzeria Ltd | Hospitality | 2023 |
| Paul & Co (Accountants) Ltd | Professional & scientific | 2018 |
| Paul Bellamy Ltd | Professional & scientific | 2013 |
| Paul Burgess Functional Medicine Ltd | Health & social care | 2019 |
| Paul Burgess Property Limited | Real estate | 2022 |
| Paul David Williams Ltd | Extraterritorial | 2024 |
| Paul Dreggs Properties Ltd | Real estate | 2024 |
| Paul Foods Ltd | Wholesale & retail | 2025 |
| Paul Lawrence Management Limited | Arts & recreation | 2008 |
| Paul Linton & Co Ltd | Professional & scientific | 2022 |
| Paul Pratt Design Services Ltd | Information & communication | 2007 |
| Paul Steward Consulting Limited | Information & communication | 2015 |
| Paulhammond.Com Ltd | Information & communication | 2023 |
| Pausable.Com Limited | Information & communication | 2024 |
| PAV Media Limited | Other services | 2009 |
| Pavani Limited | Information & communication | 2026 |
| Paveen UK Transport Ltd | Transport & logistics | 2019 |
| Paveh Limited | Real estate | 1972 |
| Pavispad Consultancy Ltd | Information & communication | 2018 |
| Pavsim Investments Limited | Real estate | 2020 |
| Pavway Limited | Hospitality | 2012 |
| Pawfect Paws Ltd | Professional & scientific | 2018 |
| Pawfully Ltd | Information & communication | 2026 |
| Paws & Pronounce Phonics Ltd | Information & communication | 2026 |
| Paws Pals Limited | Other services | 2020 |
| Pawslate Limited | Professional & scientific | 2026 |
| Pawsome Management Limited | Arts & recreation | 2023 |
| Paxman Bespoke Joinery Ltd | Construction | 2024 |
| PAY Attention Ltd | Information & communication | 2022 |
| Payback Season Movie Ltd | Information & communication | 2010 |
| Payfinora Ltd | Financial services | 2026 |
| Paza Properties Ltd | Real estate | 2020 |
| Pazarcik Ltd | Other services | 2018 |
| PB Donoghue (Green Lanes) Limited | Construction | 2017 |
| PB Mass Properties Holdings Ltd | Real estate | 2015 |
| PB Psych Ltd. | Health & social care | 2015 |
| PB Smart Facilities Management Ltd | Administrative & support | 2023 |
| PB08 Developers Ltd | Construction | 2021 |
| PBM Capital Ltd | Professional & scientific | 2022 |
| PBR Engineering Services Ltd | Construction | 2016 |
| PBS Supplies UK Ltd | Wholesale & retail | 2020 |
| PC and Mobile Solutions Ltd | Wholesale & retail | 2013 |
| PC Partners LLP | | 2022 |
| PC Wizarduk Limited | Information & communication | 2011 |
| Pccfmj Ltd | Wholesale & retail | 2025 |
| PCG Absolute Cleaning Ltd | Administrative & support | 2023 |
| PCL Technologies Limited | Information & communication | 2019 |
| Pcmgf Limited | Information & communication | 2020 |
| Pcos Marine Services Limited | Other services | 2001 |
| PCX Consultancy Limited | Information & communication | 2015 |
| PD Brew Limited | Manufacturing | 2014 |
| PD Health Ltd | Professional & scientific | 2023 |
| PD Hedges Electrical Services Limited | Construction | 2008 |
| PD UK Aesthetics Ltd | Health & social care | 2019 |
| PDB Futures Ltd | Financial services | 2007 |
| Pdfta Ltd | Information & communication | 2018 |
| PDG Consulting Ltd | Information & communication | 2023 |