BUSINESS AND ECONOMY
In the annual Budget speech, the chancellor announces tax rates and divvies up the takings according to the government's spending priorities - including how much to distribute to the nations and regions of the UK.
The government needs to secure the approval of Parliament for its Budget, although it is extremely rare for MPs to reject, or even amend, the government's plans.
UK monetary policy, once the preserve of ministers, is now set independently by the Bank of England. But the Bank works to inflation targets set by the government - and if the governor's policy fails to deliver, he must send the chancellor a letter explaining why.
Parliament retains power over UK business law throughout the UK, including competition policy, consumer protection, regulation of the post office and of financial institutions such as banks.
It also legislates for the whole of the UK on the minimum wage. But for every other aspect of employment law - including health and safety, and legislation to safeguard the rights of women, ethnic minorities and disabled people - MPs are only responsible for England, Wales and Scotland since these policy areas are devolved in Northern Ireland.
Tax rates set in Westminster apply throughout the UK, but Holyrood has the power to alter income tax rates in Scotland by up to 3p in the pound.
CULTURE, SCIENCE AND SPORT
Parliament enacts UK-wide legislation on broadcasting and gambling.
It also oversees science policy and public expenditure on scientific research across the UK.
But policy on funding the arts and sport is devolved - so Parliament controls policy for England only in these areas.
DEFENCE AND FOREIGN AFFAIRS
Policy-making on defence and international relations is not devolved, so MPs speak for the whole of the UK on these matters.
But strictly speaking, they don't have the final say on whether to sign treaties or send UK troops to war, since ultimate responsibility rests with the Queen in principle and the prime minister in practice.
Parliament does scrutinise the legitimacy and effectiveness of troop deployments, and it has been promised a vote on whether to go to war in future.
MPs also scrutinise the government's spending on defence.
And when the UK's treaty obligations need to be enshrined in domestic law, Parliament debates the new legislation.
Parliament legislates for England only in almost all education and training matters, such as providing funding for schools and universities, and setting university tuition fees.
It also decides the extent of private sector involvement in the management of English schools.
However, policies on teacher recruitment and pay, and on student loans are set in Westminster for both England and Wales.
While policy on the environment is devolved, there is co-operation between Parliament and the devolved institutions.
For example, the measures in the Westminster Climate Change Act will effectively cover the whole of the UK - with the permission of the devolved institutions (e.g. Sewel motion in Scotland).
But the devolved bodies can go further than the measures proposed by Parliament if they wish - for example, Holyrood passed a supplementary Climate Change Act for Scotland.
FARMING AND FISHERIES
In agriculture, including the distribution of EU farm subsidies, in forestry, food and fisheries, and support for rural communities, Parliament enacts legislation for England only.
For example, the Marine and Coastal Access Bill will apply to England only.
However, Westminster speaks for the whole of the UK on agricultural policy in EU negotiations.
It also regulates all UK animal exports.
Parliament legislates for the whole of the UK in some areas of healthcare with an ethical dimension, such as abortion law, surrogacy, embryology, genetics, fertilisation, xenotransplantation (the transplantation of living cells, tissues or organs from one species to another) and vivisection.
It also retains power over medicine safety (licencing of medicines) and regulation of health professions.
In all other health policy areas, power is devolved.
HOUSING AND PLANNING
Parliament has devolved power in these areas, with the exception of the regulation of buildings and the administration of Housing Benefit in Wales and Scotland (although these matters are devolved in Northern Ireland).
Decisions to grant planning permission for power stations are devolved - with the exception of power stations in Wales with a capacity of over 50 megawatts.
JUSTICE AND HOME AFFAIRS
Parliament legislates for England, Wales and Northern Ireland in these policy areas.
Westminster's relationship with Holyrood on these matters is nuanced - MPs retain the power to legislate on guns, immigration, extradition, and emergency powers in Scotland, but many other aspects are devolved.
Westminster retains oversight of local government in England only as this is a devolved issue.
Local councils throughout the UK have powers over the administration of public services such as refuse collections.
Social services are provided by local councils throughout the UK, but Parliament has ultimate responsibility for overseeing their work in England.
Parliament, by agreeing to the government's Budget, sets the levels of child benefits, tax credits, pension credits, and the disability living allowance in England, Scotland and Wales - but these policy areas are devolved in Northern Ireland.
Parliament legislates for England, Wales and Scotland (but not Northern Ireland) on: rail regulation, rail safety and rail accident investigation; and on driving tests, vehicle MoTs and certification.
It oversees the following policy areas for the whole of the UK: shipping services, marine accident investigation, coastguards, transport security, and regulation and safety of aviation, and air accident investigations, and the channel tunnel rail link.
Parliament also retains oversight of the British Transport Police for England, Wales and Northern Ireland - but not Scotland.