The government gets most of its income from taxes. For example, workers pay income tax, everyone pays VAT on certain goods, and companies pay tax on their profits.
It could, in theory, cover all of its spending from taxes, and in some years that happens.
But if it can't, it will cover the gap by raising taxes, cutting spending or borrowing.Higher taxes mean people have less money to spend, so businesses make less profit, which can be bad for jobs and wages. Lower profits also mean companies pay less tax.
So, governments often borrow to boost the economy. They also borrow to pay for big projects - such as new railways and roads - which they hope will help the economy.
Governments borrow to fund "day-to-day" spending, as well as long-term infrastructure projects like Crossrail
How does the government borrow money?
The government borrows money by selling financial products called bonds.
A bond is a promise to pay money in the future. Most require the borrower to make regular interest payments over the bond's lifetime.
UK government bonds - known as "gilts" - are normally considered very safe, with little risk the money will not be repaid.
Gilts are mainly bought by financial institutions in the UK and abroad, such as pension funds, investment funds, banks and insurance companies.
The Bank of England has also bought hundreds of billions of pounds' worth of government bonds in the past to support the economy,.
How much is the UK government borrowing?
The amount the government borrows varies from month to month.
For instance, when people submit tax returns in January, they often pay a large chunk of their annual tax bill in one go, so the government sees a jump in the amount of money it takes in.
So it is more helpful to look at the whole year, or the year-to-date.
In the 2022-23 financial year, the government borrowed £130.5bn. That was £6.1bn higher than in the previous year.
In November 2023, the government borrowed £14.3bn. This which was the fourth highest borrowing figure for November since monthly records began in 1993.
The total amount the government owes is called the national debt. It is currently about £2.67 trillion.
That is roughly the same as the value of all the goods and services produced in the UK in a year, known as the gross domestic product, or GDP.
That current level is more than double what was seen from the 1980s through to the financial crisis of 2008.
The combination of the financial crash and the Covid pandemic pushed the UK's debt up from those historic lows to its current level.
But in relation to the size of the economy, UK debt figures are still low compared with much of the last century, and also compared with some other leading economies.
How much money does the government pay in interest?
The larger the national debt gets, the more interest the government has to pay.
That extra cost was not as big when the interest rates due were low through the 2010s, but it is more noticeable now that interest rates have been rising.
If the government has to set aside more cash for paying its debts, it may mean it has less to spend on the public services which it borrowed to fund in the first place.
The amount of interest the government pays on national debt fluctuates, and by one measure,
The most significant figures tracking the cost of debt are published monthly by the Office for National Statistics (ONS).
According to this data, two months in 2022 saw record levels of money set aside for debt interest: £20bn in June and £18bn in December.
June 2023 saw the third largest monthly amount - £12.8bn.
The most recent November figure revealed interest on government debt was £7.7bn.
During the 2022-23 financial year, the government spent £108bn on debt interest - more than it spent on education.
Why does it matter if governments borrow more?
Some economists fear the government is borrowing too much, at too great a cost.
Others argue extra borrowing helps the economy grow faster - generating more tax revenue in the long run., and the negative impact is greatly exaggerated.
The OBR's latest forecasts point to a slightly slower pace of borrowing over the next few years, on average £700m less per year than forecast in March.
It now predicts that borrowing will be about £27bn lower in 2027-28 compared with its previous forecast, main due to the decision not to increase spending by government departments as inflation pushes up prices.
What is the government's plan for debt?
Chancellor Jeremy Hunt has previously said the government will take "difficult but responsible" decisions on the public finances.
He previously blamed the "twin global emergencies of a pandemic and Putin's war in Ukraine" for driving up government costs.
The chancellor has set a target of getting underlying debt to fall in five years' time.
In the Autumn Statement in November, the chancellor said the government was on track to meet the debt target.
That's because the OBR has forecast that debt as a proportion of GDP will fall in 2027-28 and 2028-29.
What is the difference between the government deficit and debt?
The deficit is the gap between the government's income and the amount it spends.
When a government spends less than its income, it has what is known as a surplus.
Debt is the total amount of money owed by the government that has built up over years.
It rises when there is a deficit, and falls in those years when there is a surplus.