O
- Oath fees
- Oaths
- Obtaining information and documents
- Occasional residence – see Residence
- Occupancy levels
- Occupation of deceased's home
- Occupational pension schemes
- Occupational Pensions Board
- Occupational therapists
- Odin Field
- OECD
- OECD Model
- OECD model tax convention
- Off-shore fields
- Off-street parking – see Local authorities and similar bodies, Parking facilities
- Offences and penalties
- Office
- Office cleaners
- Office expenditure
- Office for Standards in Education (OFSTED)
- Office holder
- Office holders
- Office of tax simplification
- Office of Tax Simplification (OTS)
- Office or employment
- Office or employment outside UK – see Period of absence
- Office-holder requirement
- Officer (of HMRC)
- Officer of a company
- Officers
- Officers of Revenue and Customs – see Commissioners and officers of Revenue and Customs, Commissioners for Revenue and Customs
- Offices
- Official agents
- Official error
- Official publications
- Official rate of interest
- Official Receiver
- Official receivers
- Official Solicitor
- Officials of the EU
- Offshore activities
- Offshore asset moves penalty
- Offshore bonds
- Offshore capital redemption policies – see Capital redemption policies
- Offshore companies
- Offshore employment intermediaries
- Offshore energy production
- Offshore exploration or exploitation activities – see Oil taxation
- Offshore funds
- Offshore funds (pre-1 December 2009)
- Offshore gas or oil installation workers
- Offshore income gains
- Offshore income, assets, activities
- Offshore income, gains and assets
- Offshore income, gains or assets
- Offshore installations
- Offshore investment companies
- Offshore investment funds
- Offshore investors
- Offshore Life Assurance Group
- Offshore non-compliance
- Offshore penalties
- Offshore tax issues
- Offshore tax non-compliance
- Offshore trusts
- OFSTED – see Office for Standards in Education (OFSTED)
- Oil
- Oil and Gas
- Oil and gas industry – see Continental shelf workers
- Oil and gas rig workers
- Oil companies
- Oil exploration or exploitation rights
- Oil extraction and related activities
- Oil field
- Oil or gas extraction
- Oil rig workers
- Oil rigs
- Oil royalties
- Oil taxation
- Ointments
- OLAB (Overseas Life Assurance Business)
- Old age allowance
- Old age and survivors' pension
- Old age pension – see Social security pension
- Old age reliefs – see Age-related allowances
- Old people's homes
- Old qualifying IP right, meaning
- Old-age pensions
- Olympic Games – see London Olympics and Paralympics 2012
- Olympic Park Legacy Company Limited
- Ombudsman
- One building and one supply
- Onerous property
- Online auction
- Online facilities
- Online filing of return – see EVAT returns
- Online marketplaces
- Online payment
- Online registration – see Registration
- Online sales of goods
- Online services – see EVAT service
- Only residence – see Residence
- Onshore field
- Onshore petroleum
- Open general import licence
- Open market value
- Open-ended investment companies (OEIC)
- Open-ended investment companies (OEICs)
- Operating leases
- Operator – see Electronic transfer systems
- Operators of sites
- Opticians
- Opting to tax – see Option to tax
- Option rights
- Option to tax
- Optional remuneration arrangements
- Options
- Options and warrants
- Orchestra tax credits
- Orchestra tax relief
- Orchestral concert
- Order in Council
- Orders
- Orders and summons
- Ordinary partnership transactions
- Ordinary residence
- Ordinary share capital – see Share capital
- Organ transplantation, therapeutic use of body parts
- Organisation for Economic Co-operation and Development
- Organisation for Economic Co-operation and Development (OECD)
- Organisations
- Organised school trips and visits
- Original shareholder
- Ornamental fish
- Ornamental fountains
- Orthoptists
- Orthotists
- Oslo and Paris Commissions
- Osteopath
- Osteopaths
- Ostriches
- Other commodities
- Other income
- Other payers
- Other Taxes
- Out-of-country supplies – see Foreign supplies
- Out-of-court settlements
- Outboard motors
- Outbuildings
- Outer space
- Outermost regions
- Outgoings – see Deductions
- Outplacement counselling
- Outplacement services for employees – see Counselling services
- Output tax
- Outputs
- Outside the scope of VAT
- Outsourcing
- Outward processing relief
- Outward processing relief (OPR)
- Outworkers
- Over-arching contracts
- Overcharged VAT
- Overdeclarations
- Overdrafts
- Overdue levy
- Overdue tax
- Overdue/overpaid tax
- Overlap profits and losses
- Overlap relief
- Overlapping leases
- Overnight expenses
- Overpaid levy
- Overpayment of tax
- Overpayment of VAT
- Overpayments
- Overriding objective of Tribunal rules
- Overriding treaties
- Overseas agencies
- Overseas authorities/bodies
- Overseas businesses
- Overseas companies – see Groups of companies, Non-resident companies
- Overseas countries and territories (OCTs)
- Overseas customers
- Overseas dividends
- Overseas electors
- Overseas employers and embassies
- Overseas employment – see Foreign income, Work done abroad, Working abroad
- Overseas estates
- Overseas funds – see Offshore funds
- Overseas government debts – see Sovereign debts
- Overseas government pensions
- Overseas governments – see Foreign governments
- Overseas income – see Foreign income
- Overseas insurers
- Overseas investigations
- Overseas leasing
- Overseas Life Assurance Business – see OLAB, Insurance companies
- Overseas life insurance companies
- Overseas losses
- Overseas medical treatment
- Overseas online retailers
- Overseas operations
- Overseas ownership
- Overseas partners
- Overseas pension schemes
- Overseas permanent establishments
- Overseas persons/traders
- Overseas properties
- Overseas property
- Overseas property business
- Overseas property businesses
- Overseas provident funds
- Overseas public service pensions
- Overseas public service schemes
- Overseas schemes
- Overseas securities – see Foreign securities
- Overseas Service Act 1958
- Overseas service pensions and pensions funds
- Overseas services – see International services
- Overseas structure
- Overseas subcontractors
- Overseas Superannuation Scheme
- Overseas suppliers
- Overseas tax – see Foreign tax
- Overseas trade debts
- Overseas trades
- Overseas transfer charge
- Overseas trusts
- Overseas visitors
- Overseas voters
- Overseas work
- Overseas workday relief
- Overseas-leasing rules
- Overtime pay
- Overview of Act
- Own-use adjustments
- Owner
- Owner occupation of property
- Owner-occupiers of property
- Ownership
- Ownership period
- Ownership structures
- Oxygen concentrators