Introduction
Most people have heard politicians talk about “the budget deficit” or “the national debt.”
These terms appear regularly in news reports, election campaigns and government announcements. They are often presented as major challenges facing the country and are frequently used to support arguments for increasing or reducing government spending.
Yet they are also two of the most commonly misunderstood ideas in economics.
Although they are closely connected, they do not mean the same thing.
In the previous pages, we learned where government money comes from and where it goes. We saw that governments collect income—known as government revenue—mainly through taxation and use that money to fund public services such as healthcare, education, defence and transport.
But what happens if the government wants to spend more money than it receives?
This is a situation that every government faces from time to time. During a recession, tax revenues may fall while demand for public services increases. A government may decide to invest in new infrastructure, respond to a national emergency or support the economy during a financial crisis. In each case, spending may temporarily exceed income.
When this happens, governments usually need to borrow money.
This is where the ideas of the budget deficit and the national debt become important.
Understanding the difference between them is one of the most valuable steps in understanding government finances. Once you grasp this distinction, many political debates and economic headlines become much easier to follow.
This page explains what a budget deficit is, what the national debt is, how the two are connected and why governments sometimes choose to borrow. It also explores why economists often disagree about how much borrowing is appropriate and why there is rarely a single correct answer.
The One Big Idea
The difference between a budget deficit and the national debt is actually quite simple.
A budget deficit describes what happens during a single financial year.
The national debt is the total amount the government owes after borrowing money over many years.
One measures what happened this year.
The other measures the result of many previous years.
An everyday example helps illustrate the difference.
No comparison between governments and households is perfect. Governments can raise taxes, borrow on a much larger scale and influence the economy in ways that households cannot. Nevertheless, the following example provides a useful way of understanding the basic relationship between a deficit and debt.
Imagine you earn £35,000 in one year but spend £37,000.
For that year, you have spent £2,000 more than you earned.
That £2,000 is your deficit.
If you borrow £2,000 to cover the shortfall, you now owe someone £2,000.
That £2,000 owed is your debt.
If the following year you again spend more than you earn and borrow another £1,000, your new deficit is £1,000, but your total debt has increased to £3,000.
The same basic principle applies to governments.
Each year’s deficit is added to the money already owed, gradually building the national debt. If a government later spends less than it receives, it may be able to reduce some of that debt.
Although governments are much larger and operate differently from households in many ways, this simple example provides a useful mental model that will help you understand the rest of this chapter.
What Is a Budget Deficit?
A budget deficit occurs when the government spends more money during a financial year than it receives in income.
Imagine that during one year the government collects £1 trillion in revenue through taxes, fees and other sources.
If it spends £1.05 trillion, it has spent £50 billion more than it received.
That £50 billion difference is the budget deficit.
The deficit does not mean that the government has run out of money or that the economy is in immediate difficulty. It simply means that, during that particular year, government spending exceeded government income.
Governments can run deficits for many different reasons.
Sometimes tax revenues fall because the economy slows and fewer people are working. Sometimes governments deliberately increase spending to support households and businesses during difficult periods. At other times they may invest heavily in projects such as transport infrastructure, schools, hospitals or energy systems that are expected to benefit the country for many years.
Some increases in government spending also happen automatically when the economy weakens. If unemployment rises or more people become eligible for financial support, government spending may increase even without any new policies being introduced.
For this reason, a deficit should not automatically be viewed as either good or bad. Like many aspects of public finance, its significance depends on why the deficit exists, how large it is and whether it can be managed responsibly over time.
It is also important to remember that a deficit refers only to one financial year.
When news reports say that “the deficit has increased” or “the deficit has fallen,” they are describing what happened during that year’s Budget. They are not describing the total amount the government owes.
That total is the national debt, which we will explore next.
Why Deficits Happen
There is no single reason why governments run budget deficits.
Sometimes a deficit results from circumstances outside the government’s control. During a recession, for example, businesses may earn lower profits, unemployment may increase and households may spend less. As a result, tax revenues often fall just as demand for public services and welfare support rises.
In other situations, governments may choose to run a deficit deliberately.
A government might decide to build new railways, hospitals or flood defences, knowing that these projects require substantial investment today but are expected to improve the country’s economy and quality of life for decades to come. Rather than paying the entire cost immediately through higher taxes, it may choose to spread the cost over many years by borrowing.
Unexpected events can also lead to deficits. Wars, natural disasters, pandemics and financial crises often require governments to spend large sums of money quickly in order to protect lives, support businesses or maintain essential public services.
Whatever the reason, a budget deficit simply describes the gap between government income and government spending during a particular year.
To understand what happens next, we need to look at the national debt.
What Is the National Debt?
If a budget deficit describes what happens during a single financial year, the national debt describes the result of borrowing over many years.
Whenever a government spends more than it receives in income, it usually needs to borrow the difference. Each year’s borrowing is then added to the money that was already owed.
The national debt is therefore the total amount the government owes as a result of borrowing over time.
An everyday example helps to illustrate the difference.
Imagine that you buy a house with a mortgage.
During one year, your household budget may not balance perfectly. You might spend slightly more than you earn because your boiler breaks down or your car needs replacing. That shortfall is similar to a budget deficit.
Your mortgage, however, is different. It is the total amount you still owe after borrowing money to buy your home. Even if your finances improve next year, the mortgage does not disappear overnight. It is repaid gradually over many years through regular repayments.
The national debt works in much the same way.
A government’s borrowing builds up over time, just as a mortgage builds up the amount that a homeowner owes. Each year’s deficit may increase the debt, while years in which the government spends less than it receives can help reduce it.
There is one important difference, however.
Unlike a household mortgage, governments do not usually aim to repay all of the national debt at once. Instead, they normally manage it over many years by repaying some borrowing while replacing other borrowing as existing loans reach the end of their term. We will look at exactly how this works in the next chapter on Government Borrowing and Bonds.
For now, the important point is simply this:
The deficit measures one year’s shortfall, while the national debt measures the accumulation of many years of borrowing.
Although governments borrow on a much larger scale than households and operate under different rules, this distinction remains one of the simplest and most useful ways of understanding public finances.
How Deficits Become Debt
The relationship between the budget deficit and the national debt becomes much easier to understand if we follow the government’s finances over several years.
Year 1
The government receives £100 billion in income but spends £110 billion.
Because it has spent £10 billion more than it received, it has a budget deficit of £10 billion.
To cover this shortfall, the government borrows £10 billion.
National debt: £10 billion
Year 2
The economy improves slightly.
Government income increases to £105 billion, but spending also rises to £112 billion.
The government now has a budget deficit of £7 billion.
It borrows another £7 billion.
National debt: £17 billion
Year 3
Income continues to grow.
The government now receives £115 billion, while spending falls slightly to £113 billion.
This time, government income is greater than government spending.
Instead of running a deficit, the government has a budget surplus of £2 billion.
It can use this surplus to repay part of its previous borrowing.
National debt falls to £15 billion.
This simple example illustrates one of the most important ideas in public finance.
The budget deficit changes every year. Some years it may be large, some years it may be small and some years there may even be a surplus.
The national debt, however, reflects the combined effect of borrowing over many years.
This is why news reports sometimes say that the deficit is falling while the national debt is still rising.
At first, this sounds confusing, but it simply means that the government is still spending more than it receives, although the gap has become smaller. As long as there is still a deficit, additional borrowing usually increases the national debt, even if it is increasing more slowly than before.
Understanding this relationship helps explain why economists pay attention to both figures. The annual deficit tells us what is happening this year, while the national debt shows the result of decisions made over many years.
Can Governments Run a Budget Surplus?
Yes.
A budget surplus occurs when government income is greater than government spending during a financial year.
Suppose the government receives £120 billion in revenue but spends £118 billion.
Instead of having a deficit, it has a budget surplus of £2 billion.
A surplus gives the government more options.
It may choose to use the money to repay some of the national debt, reduce future borrowing, build up financial reserves or invest in new projects without borrowing additional money.
However, running a surplus is not always straightforward.
Reducing government spending or increasing taxation in order to achieve a surplus may itself have economic consequences. Governments therefore have to consider not only whether they would like to reduce borrowing, but also how doing so might affect economic growth, employment and public services.
Sustained budget surpluses are relatively uncommon. Modern governments are continually investing in public services, infrastructure and the wider economy while also responding to changing economic conditions. As a result, many countries move between periods of deficits, smaller deficits and occasional surpluses rather than consistently achieving a surplus every year.
For this reason, governments do not necessarily aim to achieve a surplus every year. Instead, they try to balance many competing objectives, including maintaining public services, supporting the economy, investing for the future and keeping the public finances on a sustainable path.
Why This Distinction Matters
Understanding the difference between the budget deficit and the national debt makes it much easier to interpret political debate and economic news.
For example, if you hear that the deficit has been reduced, this does not necessarily mean that the national debt has fallen.
It simply means that the government has reduced the gap between what it spends and what it receives during that particular year.
Likewise, hearing that the national debt has increased does not automatically mean that government spending has suddenly become much higher. The increase may simply reflect another year in which spending was slightly greater than income.
Recognising this distinction helps avoid one of the most common misunderstandings in public finance.
A budget deficit is an annual measure.
The national debt is the accumulated result of borrowing over many years.
Keeping these two ideas separate provides a much clearer understanding of how government finances work and prepares us for the next question:
If governments borrow money to cover deficits, who lends them that money, and how does the borrowing process actually work?
That is the subject of the next page, Government Borrowing and Bonds.
Why Governments Run Budget Deficits
At first glance, it might seem obvious that governments should always avoid running a budget deficit.
After all, if spending more than you earn is usually discouraged in personal finance, shouldn’t the same apply to governments?
The answer is more complicated.
Governments sometimes choose to run budget deficits because they believe borrowing will benefit the country over the long term or help it through a period of economic difficulty. At other times, deficits arise because economic circumstances reduce government income faster than spending can realistically be reduced.
Understanding why deficits occur is just as important as understanding what they are.
Like many aspects of economics, the answer depends on the circumstances.
Supporting the Economy During Difficult Times
One common reason for running a deficit is to support the economy during a recession.
When economic activity slows, businesses often earn lower profits, unemployment may rise and households typically spend less money. As a result, the government usually receives less Income Tax, Corporation Tax and VAT.
At the same time, government spending often increases automatically. More people may become eligible for unemployment benefits or other forms of financial support, while governments may also choose to increase investment in public services or infrastructure to help stimulate economic activity.
This combination of lower income and higher spending frequently leads to a budget deficit.
Many economists believe that allowing borrowing to increase during a recession can reduce the severity of an economic downturn by supporting jobs, businesses and household incomes until economic conditions begin to recover.
The alternative—cutting public spending sharply or increasing taxes during a recession—may reduce borrowing in the short term but could also weaken the economy further. Governments therefore face difficult choices about how best to respond.
Investing for the Future
Governments may also choose to borrow in order to invest in projects that are expected to benefit society for many years.
Building a new railway, expanding an airport, improving flood defences or constructing hospitals and schools can require enormous amounts of money. These projects may take years to complete, but once finished they can continue benefiting millions of people for decades.
Rather than asking today’s taxpayers to pay the entire cost immediately through higher taxes, governments may decide that it is reasonable to spread the cost over many years through borrowing.
This reflects the idea that future generations, who will also benefit from these investments, should help contribute towards their cost.
This is similar to the way many people use a mortgage to buy a home. Few households could afford to purchase a house outright, but borrowing allows them to spread the cost over many years while enjoying the benefits of living in the property.
Although governments are very different from households, the principle of spreading the cost of long-lasting investments is broadly similar.
Responding to Emergencies
Unexpected events can require governments to spend very large sums of money at short notice.
Natural disasters, wars, financial crises and pandemics often demand immediate action. During these situations, waiting until sufficient tax revenue has been collected would usually be neither practical nor desirable.
For example, during the COVID-19 pandemic, governments around the world borrowed substantial amounts of money to support healthcare systems, businesses and households while large parts of their economies were temporarily closed.
Most economists agreed that these extraordinary circumstances justified extraordinary levels of borrowing because the alternative could have caused much greater economic and social damage.
Emergencies therefore illustrate one of the reasons governments borrow. In exceptional circumstances, borrowing can provide the flexibility needed to respond quickly when lives, livelihoods or national security are at risk.
Is Government Debt Always Bad?
Because the word debt often has negative associations in everyday life, it is easy to assume that the national debt must always be a problem.
In reality, the picture is more balanced.
Like many financial tools, borrowing can be either beneficial or harmful depending on how it is used and whether it remains manageable over time.
Borrowing to fund productive investments that improve the country’s future may strengthen the economy, improve public services and increase future prosperity.
Borrowing to respond to a national emergency may help protect lives, preserve jobs and reduce long-term economic damage.
However, borrowing also has costs.
The larger the national debt becomes, the more the government usually has to spend each year on interest payments. Money used to pay interest cannot be spent on healthcare, education, transport or other public services unless government income also increases.
High levels of debt may also reduce a government’s flexibility. If another economic crisis occurs, governments that already have very large debts may have fewer options available to respond.
The level of debt can also influence how investors view the country’s public finances. If lenders become less confident that borrowing is being managed responsibly, governments may have to pay higher interest rates when borrowing new money. This increases the cost of servicing the debt and can place additional pressure on future budgets.
For these reasons, most economists do not simply ask whether debt is good or bad. Instead, they ask questions such as:
- How large is the debt compared with the size of the economy?
- Why was the money borrowed?
- Is the borrowing being used productively?
- Can the debt be managed sustainably over the long term?
- Is the country likely to be able to refinance or repay its borrowing as it falls due?
These questions are often much more useful than focusing only on the total amount of debt.
Why Economists Sometimes Disagree
Economics is not like mathematics, where every problem has a single correct answer.
When economists discuss government borrowing and public debt, they often agree on the basic facts but disagree about the best course of action.
Some economists believe governments should aim to keep borrowing relatively low except during exceptional circumstances. They argue that lower debt reduces future interest payments, gives governments greater financial flexibility and lowers the risks associated with excessive borrowing.
Others believe governments should be more willing to borrow when the money is being invested wisely. They argue that borrowing to improve infrastructure, education, scientific research or new technology can strengthen the economy, making future generations wealthier and better able to manage today’s borrowing.
Many economists take a position somewhere between these views.
They may support increased borrowing during recessions but favour reducing deficits once the economy is growing strongly. Others emphasise that the quality of spending matters just as much as the amount borrowed.
These differences explain why debates about government borrowing continue even among experts.
They are rarely arguments about simple arithmetic. More often, they involve different expectations about future economic growth, different assessments of financial risk and different views about how governments should balance today’s needs with tomorrow’s responsibilities.
Importantly, these are not purely economic questions. They also involve values and priorities. How much should one generation invest for the benefit of the next? How much financial risk is acceptable? What balance should be struck between supporting today’s citizens and limiting future borrowing?
These broader questions about fairness, responsibility and the role of government will become central themes later in Fair Society.
For now, the important point is that reasonable people can disagree. One of the aims of Fair Society is not to tell readers what to think, but to help them understand why different viewpoints exist so they can reach their own informed conclusions.
Common Misunderstandings
The terms budget deficit and national debt appear regularly in news reports, political debates and election campaigns. Because they are often discussed together, it is easy to confuse them or make assumptions that are not quite accurate.
Clarifying a few common misconceptions helps make public finance much easier to understand.
“The Budget Deficit and the National Debt Are the Same Thing”
This is probably the most common misunderstanding.
A budget deficit is the amount by which government spending exceeds government income during a single financial year.
The national debt is the total amount the government owes after borrowing over many years.
A useful way to remember the difference is this:
- Budget deficit = this year’s shortfall.
- National debt = the total built up over many years.
Once you understand this distinction, many economic headlines become much easier to interpret.
“Governments Should Never Borrow”
Borrowing is often viewed negatively because many people associate debt with financial difficulty.
However, borrowing is a normal part of public finance in most developed countries.
Governments may borrow to respond to emergencies, support the economy during recessions or invest in projects that are expected to benefit society for many years. A new railway, flood defence system or hospital, for example, may continue serving the public long after the borrowing used to finance it has been repaid.
The important question is usually not whether governments borrow, but why they are borrowing and whether the borrowing remains sustainable over time.
“Governments Can Borrow Without Limit”
The opposite misunderstanding is also common.
Although governments can borrow very large sums of money, borrowing is not unlimited.
People and organisations that lend money to governments expect to be repaid. If investors lose confidence in a government’s ability to manage its finances responsibly, borrowing may become more expensive as lenders demand higher interest rates.
Higher borrowing costs mean that more public money has to be spent on interest payments, leaving less available for public services unless government income also increases.
For this reason, governments must balance the benefits of borrowing today against the responsibilities it creates for the future.
“The National Debt Has to Be Paid Off Immediately”
Another common misconception is that the national debt is like a single bill that must one day be repaid in full.
In reality, governments do not usually repay all of their borrowing at once.
Instead, borrowing is managed over many years. As some government loans reach the end of their agreed term, they are repaid or replaced with new borrowing, while governments continue managing their overall finances.
This does not mean that debt can grow indefinitely without consequences. Interest still has to be paid, and governments must continue to convince investors that their finances are being managed responsibly.
The important point is that the national debt is generally managed over time, rather than being treated as a single loan that suddenly becomes due.
The next chapter explains exactly how this process works.
“Paying Off the National Debt Should Always Be the Highest Priority”
Some people assume that governments should always aim to eliminate the national debt completely.
In practice, most developed countries carry some level of national debt over many years. Rather than trying to repay all borrowing immediately, governments usually focus on ensuring that debt remains manageable while continuing to provide public services and invest in the future.
This means that debates about the national debt are often less about whether governments should borrow and more about how much borrowing is appropriate under different economic circumstances.
“A Budget Deficit Means the Economy Is Failing”
A budget deficit does not automatically mean that the economy is performing badly.
Governments may deliberately choose to run a deficit during periods of investment or economic support. Equally, a country may experience strong economic growth while still running a modest deficit.
Similarly, a government may reduce its deficit by cutting spending or increasing taxes, but those decisions may themselves affect economic growth, employment and public services.
For this reason, economists usually consider deficits alongside many other indicators, including inflation, employment, productivity, economic growth and the overall health of the public finances.
Looking at a single figure in isolation rarely tells the whole story.
Conclusion
Governments, like households and businesses, sometimes spend more money than they receive.
When this happens, they run a budget deficit.
To finance that shortfall, they usually borrow money, adding to the national debt.
Although these two ideas are closely connected, they describe different aspects of the government’s finances.
The budget deficit measures the gap between government income and government spending during a single financial year.
The national debt measures the total amount the government owes after years of borrowing.
Understanding this distinction makes it much easier to follow political debate and economic news. It also helps explain why governments sometimes choose to borrow, why economists disagree about the appropriate level of debt and why managing the public finances involves balancing today’s needs with tomorrow’s responsibilities.
Like many topics in economics, there is rarely a simple answer that applies in every situation. Borrowing can help societies respond to crises, invest in the future and support economic growth. At the same time, excessive borrowing may increase interest costs, reduce financial flexibility and leave future governments with fewer choices.
The challenge is therefore not simply deciding whether borrowing is good or bad, but understanding when, why and how it is used.
Once you understand the difference between a budget deficit and the national debt, many discussions about government finances become much clearer. It is one of the key building blocks for understanding how modern economies work.
Continue Learning
We have now answered an important question:
What happens when government spending is greater than government income?
The next logical question is:
How do governments actually borrow money?
The next page, Government Borrowing and Bonds, explains who lends money to governments, what government bonds (known in the UK as gilts) are, why investors buy them and how governments manage borrowing over many years.
After that, How Taxes Work returns to the income side of the Budget and explains how the UK’s tax system raises the revenue needed to fund public services and support the government’s finances.
By following these pages in sequence, you are gradually building a complete understanding of the UK’s public finances:
- The UK Budget introduced the government’s financial plan.
- Where Government Money Comes From explained how government raises revenue.
- Where Government Money Goes explored how that money is allocated.
- Deficit vs Debt explained what happens when spending is greater than income.
The next two chapters complete this part of the learning journey by explaining how governments borrow and how taxation provides the income that supports the UK’s public finances.
Together, these chapters provide the foundation for understanding many of the economic and political debates that shape modern Britain.