| NTT Limited | London | A rating |
| NTT Ltd Group Services United Kingdom Limited | London | A rating |
| NTT UD Europe Ltd | London | A rating |
| NTT United Kingdom Limited t/a NTT | London | A rating |
| NUCSOFT LTD | Wembley | A rating |
| NUE OFFSHORE RESOURCES UK LIMITED | NEWBRIGE | A rating |
| Nufarm UK Limited | Bradford | A rating |
| NUMERATOR UK LIMITED | London | A rating |
| Numerus Limited | Wokingham | A rating |
| Nuriclima UK Ltd | London | A rating |
| Nurizon International Ltd. | Woking | A rating |
| Nurol Makina UK Ltd | Leamington Spa | A rating |
| NUTRICIA LIMITED | TROWBRIDGE | A rating |
| NUVAMA FINANCIAL SERVICES (UK) LTD | London | A rating |
| Nuveen Administration Limited | LONDON | A rating |
| Nuvia Ltd | Warrington | A rating |
| NVD UK Ltd | Swindon | A rating |
| NVIDIA Ltd | Reading | A rating |
| NXP Laboratories UK Limited | Glasgow | A rating |
| Nyas Technology Limited | London | A rating |
| NYK GROUP EUROPE LIMITED | London | A rating |
| NYK Trading Corporation | London | A rating |
| Nykaa International UK Limited | London | A rating |
| NYL Investments UK LLP | London | A rating |
| NYL INVESTORS (U.K.) LIMITED | London | A rating |
| NYNAS UK AKTIEBOLAG | Wirral | A rating |
| NYU in London | London | A rating |
| NZP UK Limited | Reading | A rating |
| O-I Glass Limited | HARLOW | A rating |
| O'Melveny & Myers LLP | London | A rating |
| O'Reilly Precast Limited | Barry | A rating |
| o9 Solutions UK Limited | London | A rating |
| Oakley Capital Limited | London | A rating |
| OakNorth Bank Plc | London | A rating |
| Oaktree Capital Management (UK) LLP | London | A rating |
| OANDA Europe Limited | London | A rating |
| Oando Logistics & Services Limited | London | A rating |
| Oasis Accountants Limited | London | A rating |
| Oasis Crescent Wealth (UK) Limited | London | A rating |
| Oasis Healthcare Limited | Bristol | A rating |
| Oasis Land Development Ltd | Southport | A rating |
| Oatly UK Ltd | Farringdon | A rating |
| OB UK Holdings Limited | Bromley | A rating |
| Obaseki & Co LTD | London | A rating |
| Obayashi Properties UK Limited | London | A rating |
| OBE London Limited | London | A rating |
| Oberix Group Ltd | London | A rating |
| Objective Corporation UK Ltd | Reading | A rating |
| OBJECTMASTERY (UK) LIMITED | London | A rating |
| OC&C Strategy Consultants | London | A rating |
| OCaml Labs Consultancy Limited | Cambridge | A rating |
| OCASO S.A.SEGUROS Y REASEGUROS | Godalming | A rating |
| OCCA House Ltd | Oxford | A rating |
| Occidental of Algeria LLC | London | A rating |
| OCEAN INTERNATIONAL RE LIMITED | London | A rating |
| Ocean Network Express (Europe) Limited | London | A rating |
| Ocean Partners UK Limited | Maidenhead | A rating |
| Ocean Winds UK Ltd | Edinburgh | A rating |
| Oceaneering International Services Limited | Aberdeen | A rating |
| OCLC (UK) Limited | Sheffield | A rating |
| Ocorian Services (UK) Ltd | London | A rating |
| Octispace Limited | London | A rating |
| Octopus Energy Limited | London | A rating |
| Octus Intelligence Limited | London | A rating |
| ODE Asset Management Limited | Great Yarmouth | A rating |
| Odeon Cinemas Limited | London | A rating |
| Odessa Private Limited | London | A rating |
| Odfjell Drilling Ltd | Aberdeen | A rating |
| Odfjell Technology (UK) Ltd | Aberdeen | A rating |
| Odfjell Technology Ltd | Aberdeen | A rating |
| ODL EUROPE LTD | BOOTLE | A rating |
| Odyssey Computing Limited | London | A rating |
| Odyssey Therapeutics UK Limited | Kettering | A rating |
| Off-Piste Wines Limited | Cheltenham | A rating |
| Office Holdings Limited | London | A rating |
| Office of the Free State of Bavaria in the United Kingdom | London | A rating |
| OFFICERND LIMITED | North Shields | A rating |
| OFFSET PRINT & PACKAGING LIMITED | Aylesford | A rating |
| OFS Fitel UK Ltd | Llantarnum | A rating |
| Ogab Limited | Hertfordshire | A rating |
| OGCI Climate Investments LLP | London | A rating |
| Ogier Global (UK) Limited | London | A rating |
| Ogilvy & Mathers Group (Holdings) Limited | London | A rating |
| Ohashi Technica UK Ltd | Washington | A rating |
| Ohme Operations UK Limited | London | A rating |
| OIA Global Ltd | Richmond | A rating |
| Oil & Gas Measurement Limited | Ely | A rating |
| Oilfield Production Consultants (OPC) Limited | London | A rating |
| Okala Limited | Stirling | A rating |
| Okamura Corporation, London Branch | London | A rating |
| Oki Europe Limited | Egham | A rating |
| OKI Europe Ltd | Egham | A rating |
| Okta UK Ltd | London | A rating |
| OKX UK FinTech Company LImited | London | A rating |
| OLA UK Private Limited | London | A rating |
| Olam Europe Limited | London | A rating |
| Olapic UK Limited | London | A rating |
| Olaplex UK Limited | London | A rating |
| Old Mission Europe LLP | London | A rating |
| Oldendorff Carriers (UK) Ltd | London | A rating |
| Oldham Engineering LImited | Sheffield | A rating |
| Olenick Global Ltd | Belfast | A rating |
| Oliva Health Limited | London | A rating |
| Oliver James Associates Limited | London | A rating |
| Oliver Marketing | London | A rating |
| Oliver Wyman Limited | London | A rating |
| Omaze UK Limited | London | A rating |
| Omega Flex Limited | Banbury | A rating |
| Omega Proteins Limited | Halifax | A rating |
| Omega Sinto Foundry Machinery Limited | Peterborough | A rating |
| Omega Subsea UK Limited | Westhill | A rating |
| OMERS Infrastructure Europe Limited | LONDON | A rating |
| OMERS Private Equity Europe Limited | London | A rating |
| OMICRON electronics UK Limited | Stafford | A rating |
| Omio Travel (UK) Ltd | Reading | A rating |
| OMMAX GMBH | London | A rating |
| Omni Bridgeway (UK) Limited | London | A rating |
| Omnicell Limited | Irlam | A rating |
| Omnicom Europe Limited | London | A rating |
| Omnissa (UK) Limited | London | A rating |
| Omoda & Jaecoo UK Limited | London | A rating |
| OMRON ELECTRONICS LIMITED | MILTON KEYNES | A rating |
| OMV Petrom UK Branch Office | London | A rating |
| OMV Supply & Trading Limited | London | A rating |
| On Device Solutions Ltd | Shirley | A rating |
| ONBOARD CORRUGATED LTD | WOLVERHAMPTON | A rating |
| OnboardIQ UK Limited (t/a Fountain) | London | A rating |
| ONE FLEET REALTY LTD | LONDON | A rating |
| One Group Solutions London Limited | London | A rating |
| One Investment Management Group UK Ltd | London | A rating |
| One of Us Ltd | London | A rating |
| One Source Virtual (UK) Limited | Derry | A rating |
| One Trading Exchange BV London Branch | London | A rating |
| ONEAFRICA TECHNOLOGIES LTD | MANCHESTER | A rating |
| OneChronos Markets UK Limited | London | A rating |
| Onedayone Fruit Uk Ltd | Suffolk | A rating |
| Onefootball UK Limited | London | A rating |
| Oneio Cloud UK Limited | London | A rating |
| Onepiece Jump in Ltd | London | A rating |
| OneStock Software Ltd | London | A rating |
| OneSubsea UK Limited | Leeds | A rating |
| OneTrust Technology Limited | London | A rating |
| Onex Partners Advisor UK LLP | London | A rating |
| Onfido Ltd | London | A rating |
| ONO PHARMA UK LTD | London | A rating |
| ONTARIO TEACHERS' PENSION PLAN (EUROPE) LIMITED | LONDON | A rating |
| Ontic Engineering and Manufacturing UK Ltd | Cheltenham | A rating |
| Ontier Holdings Ltd | London | A rating |
| ONTINUE UK LTD | Birmingham | A rating |
| Onward Technologies Ltd | Birmingham | A rating |
| OOCL UK Branch | Ipswich | A rating |
| Oolio Group UK Ltd | Warrington | A rating |
| Opcare Limited | Abingdon | A rating |
| Opde UK Limited | London | A rating |
| OPEC CBRNe ltd | Warrington | A rating |
| Opella Healthcare UK Limited | Reading | A rating |
| Open Box Software Limited | Rochester | A rating |
| Open Cosmos Limited | DIDCOT | A rating |
| Open Destinations Limited | London | A rating |
| Open Doors International Inc. | Witney | A rating |
| Open Health Communications LLP | Marlow | A rating |
| Open Society Foundation London | London | A rating |
| OPEN TEXT UK LIMITED | READING | A rating |
| OpenAI UK Ltd | London | A rating |
| OPENCOREOS UK LTD | London | A rating |
| OpenSymmetry Consulting Limited | London | A rating |
| OpenTable International Limited | London | A rating |
| Openwave Systems Ltd. | Belfast | A rating |
| OpenX Limited | London | A rating |
| OPERIS GROUP PLC | LONDON | A rating |
| Opia Limited | London | A rating |
| Opmobility Exterior UK Limited | Measham | A rating |
| Oppenheimer Europe Ltd | London | A rating |
| Opsec Security Limited | Washington | A rating |
| Optal Financial Limited | London | A rating |
| Optex Europe Ltd | Maidenhead | A rating |
| Optibus Transportation Limited | London | A rating |
| Optima Energy Systems Limited | Manchester | A rating |
| Optimas OE Solutions | GLOUCESTER | A rating |
| Optimatics LLC | Wood Green | A rating |
| Optimizely Ltd | London | A rating |
| Optimove UK LTD | London | A rating |
| Options Direct Ltd | richmond | A rating |
| OPTIONS GROUP (UK) LTD | LONDON | A rating |
| Options Technology Limited | London | A rating |
| Optiva Solutions (UK) Limited | Reading | A rating |
| Optiver UK Limited | London | A rating |
| Optos Plc | Dunfermline | A rating |
| Optro UK Ltd | London | A rating |
| Optum Health Solutions (UK) Limited | Buckinghamshire | A rating |
| Opus Payment Solutions UK Ltd | Milton Keynes | A rating |
| Ora Europe Ltd | London | A rating |
| Oracle Corporation UK Limited | Reading | A rating |
| Oracle Financial Services Software B.V. | London | A rating |
| Orange Brand Services Limited | London | A rating |
| Orange Business Holdings UK Limited | Slough | A rating |
| ORANGE MEDIA LIMITED | London | A rating |
| Orano Limited | Abingdon | A rating |
| Orbis Consultants Limited | London | A rating |
| Orbis Investment Advisory Limited | London | A rating |