| Northeast Shore Ltd Kinara Indian Restaurant | | | tax violations | 2019 | UK-HMRC | £26,564 |
| Northern Bespoke Developments Ltd | | | tax violations | 2023 | UK-HMRC | £40,154 |
| Northern Polymers Ltd | | | tax violations | 2019 | UK-HMRC | £773,075 |
| Northlight Surveying Ltd | | | tax violations | 2018 | UK-HMRC | £22,120 |
| Northstar Isolation Products Ltd | | | tax violations | 2019 | UK-HMRC | £20,648 |
| Norwich and Peterborough Building Society | Yorkshire Building Society | financial services | investor protection violation | 2011 | UK-FSA | £1,400,000 |
| Nota Bene Services Ltd EAB | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £2,750 |
| Nova Inc Ltd dba The Harbour | | | tax violations | 2023 | UK-HMRC | £29,388 |
| Nova Scotia Homes Ltd dba Clyde & Forth Landholdings Ltd | | | tax violations | 2018 | UK-HMRC | £33,931 |
| Novision Consulting Ltd | | | tax violations | 2024 | UK-HMRC | £160,625 |
| NP Construction Services | | | tax violations | 2024 | UK-HMRC | £23,673 |
| NPP Plastering Ltd | | | tax violations | 2021 | UK-HMRC | £388,691 |
| NRR Entertainment Limited | | | tax violations | 2018 | UK-HMRC | £51,538 |
| NSAH (Alliance Homes) Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £4,000 |
| Number One Supermarket Ltd | | | tax violations | 2019 | UK-HMRC | £37,271 |
| Numbers (UK) Ltd | | | accounting fraud or deficiencies | 2019 | UK-ICAEW | £1,138 |
| Numble Limited ASP | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £6,888 |
| Numera Partners LLP | | | accounting fraud or deficiencies | 2023 | UK-ICAEW | £480 |
| Nunes Consultant Ltd | | | tax violations | 2024 | UK-HMRC | £113,851 |
| Nurtenbirsen Limited dba Istanbul Kebab House | | | tax violations | 2021 | UK-HMRC | £40,745 |
| Nyman Libson Paul | | | accounting fraud or deficiencies | 2018 | UK-ICAEW | £4,393 |
| O'Connor Bowden Property Management (Manchester) Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £2,750 |
| O'Connor Bowden Property Management (Stockport) Limited EAB | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £3,700 |
| O'Hare News | | | tax violations | 2017 | UK-HMRC | £34,771 |
| O'Kane Bros Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £7,000 |
| O'Reilly Contract Scaffolding Ltd | | | tax violations | 2022 | UK-HMRC | £107,682 |
| O.B. Gallery Limited | | | tax violations | 2019 | UK-HMRC | £125,393 |
| O.C.O. Glenrothes Limited dba Pizza Hut Franchise | | | tax violations | 2019 | UK-HMRC | £19,351 |
| O.S.L | | | tax violations | 2017 | UK-HMRC | £127,957 |
| Oaklands Estates Ltd EAB | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £2,526 |
| Oakleigh House Farm Ltd | | | tax violations | 2023 | UK-HMRC | £49,326 |
| Oakmount Law Solicitors | | | anti-money-laundering deficiencies | 2023 | UK-SRA | £3,720 |
| Oakwood Letting & Estates Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £7,350 |
| Oasis Catering Limited | | | tax violations | 2023 | UK-HMRC | £189,868 |
| Oatcakes & Milkshakes Ltd | | | tax violations | 2024 | UK-HMRC | £35,949 |
| Oatfield Developments Ltd | | | tax violations | 2020 | UK-HMRC | £309,846 |
| Obaseki & Co Ltd | | | anti-money-laundering deficiencies | 2024 | UK-SRA | £9,000 |
| OBC Group Ltd. fka Orchard Brickwork and Construction Ltd. | | | tax violations | 2022 | UK-HMRC | £69,168 |
| OBC The Accountants Limited | | | accounting fraud or deficiencies | 2018 | UK-ICAEW | £850 |
| Ocean Trawl Grimsby Limited | | | tax violations | 2021 | UK-HMRC | £92,957 |
| Octane Holding Group Limited | | | tax violations | 2024 | UK-HMRC | £140,974 |
| Ocwen Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £6,300 |
| Odukuly Ltd ASP | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £2,750 |
| Odyssey Construction Services Limited | | | tax violations | 2023 | UK-HMRC | £145,888 |
| Office Serv Limited TCSP | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £5,100 |
| Okrich Private Ltd franchise of Rollover | | | tax violations | 2017 | UK-HMRC | £78,007 |
| Olaiya African Food Store Ltd. | | | tax violations | 2023 | UK-HMRC | £23,361 |
| Old Hong Kong Ltd | | | tax violations | 2018 | UK-HMRC | £55,190 |
| Oldland Consulting Limited ASP | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £13,500 |
| Oliver & Akers Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £14,182 |
| Oliver Clive & Co Limited | | | accounting fraud or deficiencies | 2024 | UK-FRC | £262,692 |
| Ollie's Kebab & Pizza Limited fka Farnborough Pizza & Kebab Centre Limited. | | | tax violations | 2023 | UK-HMRC | £24,389 |
| Olympus Eyewear Europe Ltd | | | tax violations | 2019 | UK-HMRC | £85,766 |
| OME (HR Management) Corporation Ltd dba CTS Personnel Ltd. | | | tax violations | 2017 | UK-HMRC | £45,575 |
| Omega Plus Ltd dba Dynasty Chinese | | | tax violations | 2018 | UK-HMRC | £307,725 |
| On Point Reviews Ltd | | | tax violations | 2023 | UK-HMRC | £273,986 |
| On Site Recruitment Solutions Ltd | | | tax violations | 2021 | UK-HMRC | £174,637 |
| On The Move Estate Agents Ltd EAB | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £6,000 |
| On Yip Restaurant Limited dba Hup Lee Buffet | | | tax violations | 2019 | UK-HMRC | £77,304 |
| One Local, Barringer Road | | | tax violations | 2024 | UK-HMRC | £18,486 |
| One Minute Security Limited | | | tax violations | 2024 | UK-HMRC | £841,994 |
| Onestopmoneymanager Ltd | | | tax violations | 2022 | UK-HMRC | £64,139 |
| OnTax Accountants Ltd ASP | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £2,750 |
| Ooki Takeaway Limited | | | tax violations | 2016 | UK-HMRC | £14,212 |
| Opal Partners Limited EAB | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £23,400 |
| Opco Leisure Ltd dba Casa | | | tax violations | 2022 | UK-HMRC | £70,417 |
| OPP Group Ltd | | | tax violations | 2021 | UK-HMRC | £325,707 |
| OPR Sports Management Ltd fka OPR Sports Consultancy Ltd | | | tax violations | 2018 | UK-HMRC | £32,300 |
| Optimum Probate and Estate Administration | | | accounting fraud or deficiencies | 2023 | UK-ICAEW | £525 |
| Orbis Wines and Spirits Limited dba Ds Warehouse | | | tax violations | 2016 | UK-HMRC | £17,078 |
| Orbit Hosting Ltd | | | tax violations | 2019 | UK-HMRC | £64,032 |
| Orchard Accountancy Services Limited ASP | | | anti-money-laundering deficiencies | 2021 | UK-HMRC | £10,030 |
| Oriental Express | | | tax violations | 2018 | UK-HMRC | £98,560 |
| Oriental Kitchen (Purley) Limited | | | tax violations | 2020 | UK-HMRC | £53,504 |
| Original 7 Spices Ltd | | | tax violations | 2023 | UK-HMRC | £19,489 |
| Originals SP Zo.o | | | tax violations | 2023 | UK-HMRC | £1,856,628 |
| Orinsen Limited EAB | | | anti-money-laundering deficiencies | 2021 | UK-HMRC | £13,100 |
| Orlandomagic Ltd | | | tax violations | 2024 | UK-HMRC | £478,279 |
| Ormeau 2016 Limited dba CBSWM12 Limited dba CBS Astor Buller Limited | | | tax violations | 2016 | UK-HMRC | £19,958 |
| Osborne & Allen Limited AMP | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £3,200 |
| Oshin Properties Ltd EAB | | | anti-money-laundering deficiencies | 2023 | UK-HMRC | £11,400 |
| Ossies Fish and Chips Ltd | | | tax violations | 2019 | UK-HMRC | £122,371 |
| OTGP HK Trading Ltd | | | tax violations | 2021 | UK-HMRC | £822,910 |
| Otis Bier Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £3,100 |
| Otium Swindon Ltd dba Bushwackers | | | tax violations | 2016 | UK-HMRC | £31,258 |
| Otium Worcester Limited | | | tax violations | 2016 | UK-HMRC | £28,049 |
| Ours Home Asset Management Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £6,313 |
| Outernational Limited | | | tax violations | 2024 | UK-HMRC | £21,054 |
| Ovenden Polski Skelp | | | tax violations | 2023 | UK-HMRC | £24,216 |
| Oxford Academy of Management Limited ASP | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £2,736 |
| Oxford Accountants for Business Limited ASP | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £4,500 |
| Oxford Seating Company Ltd dba Chairtrader Ltd. | | | tax violations | 2016 | UK-HMRC | £12,453 |
| P & G Partnership | | | tax violations | 2023 | UK-HMRC | £111,826 |
| P & G Partnership | | | tax violations | 2023 | UK-HMRC | £89,742 |
| P & M McCann (Flooring Specialists) Ltd | | | tax violations | 2021 | UK-HMRC | £63,288 |
| P A Baxter & Son Ltd | | | tax violations | 2018 | UK-HMRC | £59,290 |
| P D Properties & Investments Ltd | | | tax violations | 2021 | UK-HMRC | £142,450 |
| P E S Trading Ltd | | | tax violations | 2017 | UK-HMRC | £50,017 |
| P J West London Limited fka Papa John's West London Limited franchise of Papa John's | | | tax violations | 2018 | UK-HMRC | £37,501 |
| P K Properties (London) Limited EAB | | | anti-money-laundering deficiencies | 2022 | UK-HMRC | £2,750 |
| P L Design and Build Limited | | | tax violations | 2016 | UK-HMRC | £16,623 |
