What If Your Biggest Customer Left Tomorrow?
How stress testing helps established businesses prepare for the unexpected.
Part 3 of our Business Resilience Series
Introduction
Imagine arriving at work tomorrow morning to discover that your biggest customer has gone into administration.
Overnight, you’ve lost 35% of your turnover.
Payroll is due in three weeks. Suppliers still expect to be paid. Your bank loan repayment is approaching. Cash is already tight.
What would you do first?
For many business owners, the honest answer is, “I’m not sure.”
The most resilient businesses aren’t necessarily the ones that avoid problems. They’re the ones that have already thought through the difficult questions and prepared a plan before a crisis happens.
That’s what stress testing is all about.
No one can predict the future, but every business owner can prepare for it.
Part of Our Business Resilience Series
In our article “Small Business in a Riskier World: 6 Ways to Survive Bad Times,“ we explored why today’s business environment is more unpredictable than ever before. We identified six practical ways established SMEs can strengthen their resilience and continue to thrive despite economic uncertainty.
This article explores the third of those six ways: stress testing your business.
In the first two articles, we looked at:
- Business Strategy for SMEs: How to Stay Competitive in an Uncertain Economy – why having a clear strategy helps businesses adapt to changing markets.
- Cashflow: The Lifeblood of Your Business in an Uncertain World – why healthy cash flow provides the financial resilience every business needs.
Now we turn to another essential question.
If something unexpected happened tomorrow, how well prepared would your business really be?
Stress testing isn’t about expecting the worst. It’s about understanding how your business would cope under pressure, identifying potential weaknesses before they become serious problems, and putting practical plans in place to protect everything you’ve worked so hard to build.
Could Your Business Pass the Five-Minute Stress Test?
Before you read any further, answer these questions honestly.
- If we lost our largest customer tomorrow, would we know exactly what to do?
- Could our business survive a 20% fall in sales for three months?
- Do we know how long our cash reserves would last?
- Have we identified our five biggest business risks?
- Have we reviewed our contingency plans during the last year?
If you answered “No” or “I’m not sure” to any of these questions, this article is for you.
Why Stress Testing Matters More Than Ever
Most business owners spend their time thinking about growth.
How can we win more customers?
How can we recruit the right people?
How can we increase profitability?
These are all important questions.
But there’s another question that deserves just as much attention.
What happens if things don’t go according to plan?
For established businesses, the risks are becoming more numerous and often more interconnected than ever before.
Inflation may be easing, but costs remain significantly higher than they were only a few years ago. Interest rates have increased borrowing costs, supply chains continue to experience disruption, cyber-attacks are becoming more sophisticated, and geopolitical events can affect businesses thousands of miles away almost overnight.
Closer to home, many businesses are heavily dependent on a small number of customers, suppliers or key employees. Losing just one of them could have a significant impact.
None of these risks are unusual.
They are simply part of doing business today.
The difference is that some businesses prepare for them, while others hope they never happen.
What Is Stress Testing?
Stress testing is simply the process of asking “What if?”
What if sales fell by 20%?
What if your biggest customer stopped trading?
What if operating costs increased unexpectedly?
What if a cyber-attack prevented your business from operating for a week?
Rather than trying to predict exactly what will happen, stress testing examines how your business would perform under a range of challenging but realistic scenarios.
It is a structured way of understanding your vulnerabilities before they become problems.
Large financial institutions have used stress testing for many years because regulators require them to demonstrate they can survive severe economic shocks.
The principle is exactly the same for SMEs.
The difference is that it doesn’t require complex financial models or specialist software.
A well-designed spreadsheet, good financial information and some honest conversations are often enough to reveal where your business is most exposed.
The Purpose Isn’t to Predict the Future
One of the biggest misconceptions about stress testing is that it’s about predicting the next crisis.
It isn’t.
No one knows what the next challenge will be.
Five years ago, few businesses predicted a global pandemic.
Equally, few predicted the speed at which inflation would rise, how quickly interest rates would increase, or how disruptive cybercrime would become.
Trying to predict the future is impossible.
Preparing for uncertainty is not.
That is why stress testing is such a valuable management discipline.
Businesses that have already considered different scenarios usually respond faster, make better decisions and avoid panic when circumstances change.
Instead of reacting emotionally, they already have options.
Instead of asking, “What do we do now?”, they’re asking, “Which of our contingency plans do we implement first?”
That difference can determine whether a business experiences a temporary setback or a long-term crisis.
Start by Challenging Your Assumptions
Every successful business is built on assumptions.
You may assume that sales will continue at current levels.
You may assume customers will continue paying within agreed terms.
You may assume your key supplier will always be able to deliver.
You may assume your operations Director will always be there.
Stress testing begins by challenging those assumptions.
Ask yourself questions such as:
- What if sales fell by 20%?
- What if operating costs increased by 20%?
- What if our largest customer stopped buying from us?
- What if interest rates increased again?
- What if a cyber-attack prevented us from trading for several days?
- What if one of our key suppliers failed?
- What if one of our senior managers left unexpectedly?
These aren’t pessimistic questions.
They’re practical ones.
The businesses that survive periods of uncertainty aren’t necessarily those with the highest profits.
They’re often the ones that asked the difficult questions before circumstances forced them to.
Turning “What If?” into Practical Action
Asking “What if?” is only the first step.
The real value of stress testing comes from understanding how different events could affect your business and deciding what you would do if they happened.
The good news is that stress testing doesn’t have to be complicated. You don’t need sophisticated software or pages of financial models. The aim isn’t to create the perfect forecast; it’s to identify the risks that could have the greatest impact on your business and prepare for them.
Where Should You Start?
Every business is different, so every stress test should reflect the specific risks faced by that business.
A manufacturer has different concerns from a professional services firm. A construction company faces different challenges from a retailer. Family businesses often have additional considerations around key people and succession planning.
Start by identifying the assumptions your business depends on every day.
For example:
- How much do you expect to sell each month?
- How quickly do customers normally pay?
- Are you relying heavily on one or two major customers?
- How dependent are you on one supplier?
- Could the business continue to operate if a key employee was unavailable?
- How much spare cash does the business have if income suddenly falls?
Once you’ve identified those assumptions, start asking one simple question:
“What if that assumption turned out to be wrong?”
You’ll often be surprised how quickly potential vulnerabilities begin to emerge.
Focus on Plausible Scenarios
The purpose isn’t to imagine every disaster imaginable.
It’s to think about events that are challenging but entirely realistic.
Examples include:
- Sales falling by 20%
- Operating costs increasing by 20%
- Losing your largest customer
- Losing a key employee
- Customers taking twice as long to pay
- A major supplier failing
- A cyber attack preventing trading for several days
- Interest rates increasing further
- A serious equipment failure
- Unexpected regulatory or tax changes
None of these scenarios are extreme.
Many businesses have experienced one or more of them during the past few years.
The question isn’t whether these things could happen.
It’s whether your business is prepared if they do.
Real Life Doesn’t Happen One Problem at a Time
One of the biggest mistakes businesses make is testing risks individually.
Real life doesn’t work like that.
Imagine this scenario.
Sales fall because one of your largest customers reduces its orders.
At the same time, suppliers increase their prices.
Then two customers delay paying their invoices.
Suddenly, you’re dealing with three separate problems that all affect cash flow at exactly the same time.
This is why multi-factor stress testing is often far more valuable than looking at risks in isolation.
It provides a much more realistic picture of how resilient your business really is.
As the owner of your business, you’re best placed to identify which combinations of events would have the greatest impact.
Stress Testing in Practice
Sometimes the easiest way to understand stress testing is to see how it works in real businesses.
Example 1 – Manufacturing Business
A manufacturing business sources around 60% of its components from one overseas supplier.
Political disruption delays deliveries for six weeks.
At the same time, energy prices increase significantly.
Production slows.
Customer orders are delayed.
Cash receipts begin to fall.
Fortunately, the business had already carried out a stress test covering supply chain disruption and rising operating costs.
As a result, it had already:
- identified alternative suppliers
- increased stock levels of critical components
- arranged additional working capital funding
Instead of reacting in panic, management simply implemented the contingency plan.
The disruption was significant.
The crisis was avoided.
Example 2 – Consultancy Business
A successful consultancy generates almost half of its annual income from one long-standing client.
Without warning, the client announces a major cost-cutting programme and terminates several contracts.
Because the consultancy had previously modelled this scenario, management already knew what actions to take.
Management immediately:
- reduced discretionary spending
- accelerated business development activity
- focused on existing client relationships
- used a pre-agreed overdraft facility to manage cash flow while replacing lost income
Planning ahead meant valuable time wasn’t lost deciding what to do.
Example 3 – Retail Business
A retailer has significant borrowing on a variable interest rate.
A stress test reveals that another increase in interest rates would remove most of the company’s annual profit.
Rather than waiting for rates to rise again, the owner decides to refinance part of the borrowing onto a fixed rate and gradually build larger cash reserves.
The additional planning creates greater certainty and reduces future financial risk.
The Best Investment You May Never Need
Some business owners worry that preparing for events that may never happen is time wasted.
In reality, it’s usually one of the best investments they can make.
The time and money spent identifying vulnerabilities, strengthening weak areas and preparing contingency plans is almost always far less than the cost of dealing with an unexpected crisis without any preparation.
Think of it in the same way as business insurance.
You hope you’ll never need it.
But you’re very glad it’s there if you do.
Stress testing works in much the same way.
It gives you confidence that, whatever happens, you’ve already considered your options.
A Valuable Discussion for Every Leadership Team
One of the greatest benefits of stress testing isn’t the spreadsheet.
It’s the conversation.
When directors and senior managers sit together and ask difficult questions, they often uncover risks that nobody had previously recognised.
Different people see different threats.
Finance may focus on cash flow.
Operations may identify supply chain issues.
Sales may recognise customer concentration risks.
IT may highlight cyber vulnerabilities.
Bringing those perspectives together creates a far more complete picture of the business and often leads to better decisions long before problems arise.
From Planning to Action
Identifying potential risks is only half the exercise.
The real value of stress testing comes from what you do next.
Every significant scenario should lead to at least one practical action that makes your business more resilient. The aim isn’t to eliminate every risk—that’s impossible. It’s to reduce the impact of those risks and give yourself more options if the unexpected happens.
The businesses that recover most quickly from setbacks aren’t always the biggest or the most profitable. They’re often the ones that have thought ahead and already know their next move.
Turning Scenarios into Contingency Plans
Every stress test should answer an important question:
“If this happened tomorrow, what would we actually do?”
The answer should never be, “We’ll work it out when the time comes.”
Instead, each scenario should result in a simple contingency plan.
Depending on the risks you’ve identified, that might include:
- reducing discretionary expenditure if sales fall below an agreed level
- diversifying your customer base to reduce reliance on one or two major clients
- identifying alternative suppliers before they’re needed
- improving cyber security and data back-up procedures
- arranging additional finance while your business is in a strong position
- reviewing insurance cover to ensure it remains appropriate
- strengthening your business continuity plan
- building larger cash reserves during profitable periods
Most of these actions don’t require major investment.
Many simply require forward planning.
Small improvements made today can significantly reduce the impact of future problems.
You Don’t Need Complex Financial Models
One of the biggest misconceptions about stress testing is that it requires specialist software or sophisticated forecasting tools.
For most SMEs, that’s simply not the case.
A well-designed spreadsheet is often all you need.
Start with your monthly figures for:
- sales
- direct costs
- overheads
- cash inflows
- cash outflows
- loan repayments
- VAT and tax liabilities
Then begin changing the assumptions.
What happens if sales reduce by 20%?
What if customers take an extra 30 days to pay?
What if payroll increases because you need to recruit?
What if your energy costs rise again?
What if two of these events happen at the same time?
As you adjust each assumption, pay particular attention to three areas.
Profitability
Would the business remain profitable?
If not, how long could losses continue before corrective action became necessary?
Cash Flow
Many profitable businesses fail because they run out of cash.
Would your business still have sufficient cash to meet wages, supplier payments and tax liabilities?
If not, when would cash become critical?
Borrowing Requirements
Would existing banking facilities still be sufficient?
Would additional funding be needed?
Would it be better to discuss finance with your bank now rather than during a crisis?
These questions are often far more valuable than producing a perfectly accurate forecast.
Review Your Stress Tests Regularly
Stress testing should never be a one-off exercise.
Businesses evolve.
Markets change.
Economic conditions shift.
The risks facing your business today may be very different from those you faced twelve months ago.
For that reason, it’s good practice to review your stress testing regularly.
For many established SMEs, a quarterly review is sufficient.
You should also revisit your stress tests whenever there is a significant change within the business, such as:
- winning or losing a major customer
- making a significant investment
- taking on additional borrowing
- entering a new market
- acquiring another business
- recruiting key members of staff
- changes in legislation or taxation
Keeping your scenarios up to date means your contingency plans remain relevant.
Don’t Keep It in Your Head
Many experienced business owners have contingency plans.
The problem is that those plans often exist only in their heads.
That creates unnecessary risk.
If the owner is unavailable because of illness, an accident or another unforeseen event, would the rest of the management team know what to do?
Documenting your stress tests and contingency plans makes your business less dependent on one individual.
It also creates confidence throughout the organisation.
Everyone understands the priorities.
Everyone understands the response.
And everyone is better prepared if difficult decisions need to be made quickly.
Evidence Builds Confidence
Stress testing isn’t just valuable internally.
Increasingly, it also provides reassurance to people outside your business.
Banks and other lenders want confidence that borrowers understand the risks they face.
Customers want confidence that critical suppliers will continue to deliver.
Suppliers want confidence that customers remain financially stable.
Investors want confidence that management is thinking beyond next month’s results.
Being able to demonstrate that your business regularly reviews risks, tests different scenarios and implements practical contingency plans sends a powerful message.
It shows that your business is proactive rather than reactive.
Prepared rather than hopeful.
Professional rather than complacent.
As we’ve said throughout this series:
Evidence of action is always more powerful than words.
Resilience Is Becoming a Competitive Advantage
For many years, resilience was viewed as good business practice.
Today, it’s becoming something much more valuable.
A competitive advantage.
Customers increasingly want to work with suppliers they can rely on.
Lenders prefer businesses that demonstrate sound financial management.
Employees are more likely to stay with organisations that are well led and prepared for uncertainty.
The businesses that continue investing in planning, governance and financial discipline are often the same businesses that emerge stronger after periods of economic uncertainty.
Resilience doesn’t simply help businesses survive.
It gives them the confidence to grow while competitors are focused on reacting to events.
You Don’t Have to Do It Alone
As businesses grow, they become more complex.
The systems, processes and experience that were enough when turnover was £250,000 may no longer be sufficient when turnover reaches £2 million or £10 million.
This is where trusted advisers add real value.
Your accountant can help challenge financial assumptions, model different scenarios and identify potential pressure points before they become serious problems.
Your bank can discuss funding options while your business remains in a strong financial position.
Experienced advisers and non-executive directors can often identify risks that those closest to the business simply don’t see.
Sometimes the most valuable question is the one an independent adviser asks.
A fresh perspective often uncovers opportunities and vulnerabilities that management has overlooked.
Preparing for uncertainty doesn’t mean expecting the worst.
It means giving your business the best possible chance of navigating whatever comes next.
Preparing Today for Tomorrow’s Challenges
Every successful business owner accepts that uncertainty is part of running a business.
The question isn’t whether challenges will arise.
The question is whether your business will be ready when they do.
Stress testing doesn’t eliminate risk, but it does reduce uncertainty. It gives you a clearer understanding of where your business is most vulnerable and the confidence that comes from knowing you’ve already considered your options.
Businesses that prepare for difficult circumstances are rarely caught completely off guard. They have thought through the risks, agreed practical responses and identified the actions they would take if circumstances changed.
That preparation can make the difference between a temporary setback and a crisis.
A Stronger Business Starts with Better Questions
Many business owners spend time reviewing last month’s performance.
Fewer spend time asking questions about the future.
Yet some of the most valuable questions you can ask are also the simplest.
- What if sales reduced significantly?
- What if one of our key customers left?
- What if costs increased faster than expected?
- What if our systems were unavailable for several days?
- What if a key member of the team was unable to work?
- Would we know exactly what to do?
If those questions are difficult to answer, they have already highlighted an opportunity to strengthen your business.
Stress testing is not about finding fault.
It’s about giving yourself time to prepare while you still have choices.
Preparing for Uncertainty Is Good Leadership
One of the most important responsibilities of any business owner is protecting the organisation they’ve worked so hard to build.
That means looking beyond today’s workload and considering tomorrow’s challenges.
Employees depend on the business for their livelihoods.
Customers rely on it to deliver.
Suppliers rely on it to honour its commitments.
Preparing for uncertainty isn’t simply good financial management.
It’s good leadership.
Business owners who invest time in planning ahead are often better placed to make calm, informed decisions when circumstances change.
Instead of reacting under pressure, they’re implementing plans they’ve already discussed and agreed.
Why Professional Advice Makes a Difference
Stress testing works best when assumptions are challenged objectively.
It’s easy to become optimistic about our own businesses.
Sometimes we’re simply too close to see potential weaknesses.
That’s where experienced advisers add real value.
A trusted accountant can help you:
- challenge financial assumptions
- model realistic scenarios
- identify areas of vulnerability
- assess the impact on cash flow and profitability
- develop practical contingency plans
- strengthen the financial resilience of your business
Equally important, an independent adviser brings experience gained from working with many different businesses across a range of sectors.
They’ve often seen similar challenges before and can help you prepare for situations you may not yet have considered.
Resilience Isn’t About Standing Still
Preparing for uncertainty doesn’t mean becoming cautious or avoiding growth.
Quite the opposite.
Businesses that understand their risks are often better positioned to invest, expand and seize new opportunities because they know their financial limits and understand the potential consequences of different decisions.
Confidence doesn’t come from believing nothing will go wrong.
It comes from knowing your business is prepared if it does.
That’s what resilience really means.
Final Thoughts
No one can predict the next economic shock.
No one knows when a key customer might leave, costs might rise unexpectedly or disruption might affect the way businesses operate.
What business owners can do is prepare.
Stress testing gives you the opportunity to ask difficult questions before circumstances force you to answer them.
It helps you understand where your business is strongest, where it is most exposed and what practical steps you can take to improve resilience.
The businesses that thrive over the long term are not always the biggest, the fastest growing or the most profitable.
More often, they are the businesses that combine ambition with preparation.
They plan ahead.
They review their assumptions.
They adapt when circumstances change.
And they make decisions based on evidence rather than hope.
In an increasingly uncertain world, asking “What if?” may be one of the most valuable habits any business owner can develop.
A few hours spent stress testing your business today could help protect everything you’ve spent years building.
How RMC Accountants Can Help
At RMC Accountants, we work with established owner-managed and family-run businesses across the UK to build stronger, more resilient organisations.
We understand that today’s business owners need more than compliance services. They need a trusted adviser who can help them navigate uncertainty, challenge assumptions and make confident decisions.
Whether you’re looking to strengthen your cash flow, model different business scenarios, improve financial visibility or develop practical contingency plans, we’re here to help.
If you’d like to understand how resilient your business really is, we’d be delighted to arrange an initial, no-obligation discussion.
Together, we can help ensure your business is prepared not just to survive uncertainty, but to emerge stronger because of it.