It has been held every year since 1978, and on March 5 specifically for the past two decades, but this year it has been rescheduled to May 22.
Finance minister Rishi Sunak will present the budget in parliament around 1230 GMT.
In Britain, Sajid Javid's resignation sent London's benchmark FTSE 100 index down.
The EU's poorer members, also agreed to fight any move to cut the EU Cohesion Fund reserved for the bloc's weaker economies.
The chancellor said in his Budget speech to parliament that Britain is now "the world's sixth-largest economy".
Policymakers must stop pretending they can fix broken markets with more and more regulation.
Think tank says Philip Hammond's decision to cut stamp duty is a 'very poor way to boost home ownership'.
After Chancellor Philip Hammond announced that stamp duty will be abolished for most first-time buyers, young people reacted with mixed feelings.
Chancellor Philip Hammond downgrades economic forecasts and unveils appealing policy morsels.
Chancellor pledges to invest £44bn to revive Britain's housing sector and delivers £3.75bn boost to NHS.
Corbyn said that pay was lower than it was in 2010 and wages were falling, also claiming that economic growth was the lowest since 2009.
Downing Street fears that the Budget will fall flat as ties between prime minister Theresa May and chancellor Philip Hammond feel the strain.
Tax breaks for companies that make a concrete effort to employ released prisoners would benefit both jails and the economy.
Chancellor Philip Hammond wants UK to be at the forefront of technology after leaving the European Union.
Three years of growth have come to a stuttering halt as events in 2017 dented the confidence of marketing bosses.
Think tank says annual cost of raising public sector pay in line with consumer price inflation would be £3.3bn by 2019/20.
PM and chancellor at odds in policy squabble dating back to Budget.
Medicines, dental work, stamps, council taxes and utilities are all more expensive from today.
Fresh hints that Trump could agree to a budget without funding for wall.
Prime Minister Theresa May will hope to get on the front foot after a triple whammy of bad news.
Nasa responds to Donald Trump's budget - it will use the money to fly as far away from him as it can
Space agency said it would be 'reshaping' its focus based on the resources available.
Chancellor was forced into embarrassing U-turn over National Insurance hike for the self-employed.
Of 15 Cabinet agencies, 12 face deep cuts while boosting money for the military, law enforcement, private education.
Tories had promised not to raise VAT, income tax or NICs in their 2015 general election manifesto.
American industries say they're hopeful the cash will come to fix the nation's crumbling roads and rail... eventually.
Philip Hammond is addressing a genuine problem with how the self-employed are taxed.
Research shows that Chancellor Philip Hammond's Budget increase in NIC plus cuts in universal credit would hit single-parent families hardest.
Boost for embattled Chancellor Philip Hammond as voters continue to back the Conservatives.
Former prime minister had pledged Conservatives would not raise National Insurance contributions.
However the policy will not be debated until after the autumn statement.