There is no single correct amount of cash that every small business should keep in reserve.

You will often hear rules such as:

Three months of expenses.

Or:

Six months of overheads.

Those aren't useless starting points.

But they become dangerous when treated as universal answers.

A business with recurring monthly revenue, hundreds of customers, low fixed costs and customers paying by card has a completely different cash risk from a contractor employing 30 people, funding materials upfront and waiting 60 days for three major customers to pay.

They should not hold identical reserves simply because their turnover happens to be similar.

A better answer is:

Your cash reserve should be large enough to cover the realistic gap between something going wrong and the business having enough time to respond properly.

For many established small businesses, testing the business against two to three months of essential cash outgoings is a sensible starting exercise.

Then move that number up or down according to your actual risk.

Not turnover.

Not ego.

Not whatever somebody on LinkedIn said every business should have in the bank.

Your business.

Cash reserve is not the same as having money in the bank

This distinction matters.

Imagine your bank account contains £180,000.

Sounds healthy.

But during the next eight weeks you have:

• £75,000 of payroll
• £30,000 owed to suppliers
• £18,000 of VAT and other tax liabilities
• £12,000 of finance payments and rent
• £20,000 required to purchase materials for confirmed work

That £180,000 is not a £180,000 reserve.

Much of it already has a job.

A genuine reserve is the money available after allowing for the ordinary cash requirements and known liabilities of the business.

That is why I would never look at a bank balance in isolation and announce:

“We've got loads of cash.”

You might.

Or you might simply be looking at tomorrow's money sitting temporarily in today's account.

Cash reserve and working capital are different

They overlap, but they are not quite the same thing.

Working capital is what the business needs to keep operating normally.

You pay wages.

You buy stock.

You purchase materials.

You deliver work.

You pay rent, software, utilities and finance agreements.

Then, depending on the business model, you may wait days, weeks or months before the customer pays you.

The British Business Bank describes working capital as the money required to operate day to day and emphasises that the longer your cash-flow cycle, the more capital you are likely to need. It also warns that profitable businesses can still run into serious difficulties when they cannot meet short-term liabilities.

That money is not really your emergency reserve.

It is the fuel required for normal trading.

Your cash reserve sits behind that.

Think of it as financial shock absorption.

Start with your essential monthly cash outgoings

If income disappeared tomorrow, what would the business still have to pay?

Not every cost on your profit and loss account.

I mean the things you could not immediately stop without serious consequences.

Depending on the business, that might include:

• Payroll
• Employer employment costs
• Rent
• Business rates
• Utilities
• Essential software
• Insurance
• Finance agreements
• Loan repayments
• Minimum contractual supplier commitments
• Essential vehicle costs
• Professional fees
• Minimum owner/director drawings or salary requirements
• Critical subcontractors
• Other unavoidable operating costs

Separate these from genuinely discretionary spending.

Advertising may be reducible.

A planned office refurbishment can probably wait.

A new machine might be postponed.

A conference booking can be cancelled.

Twenty employees' wages cannot simply disappear because sales had a bad month.

Let's imagine the business normally spends £100,000 every month.

But only £65,000 is truly unavoidable in the short term.

If you decide you want three months of essential operating cover, your starting reserve calculation is not:

£100,000 × 3 = £300,000

It is closer to:

£65,000 × 3 = £195,000

We are already producing a considerably more useful number.

But we're not finished.

Then understand your cash-flow cycle

This can completely change the answer.

Consider two businesses.

Business A

Customers pay immediately by card.

Suppliers provide 30-day terms.

Stock turns quickly.

Revenue is spread across thousands of transactions.

Business B

Employees and suppliers are paid throughout the month.

Large projects take six weeks to deliver.

Invoices are raised after completion.

Customers then pay on 60-day terms.

Three customers represent half of annual revenue.

These businesses could make exactly the same annual profit.

Business B should almost certainly think much more seriously about liquidity.

British Business Bank guidance recommends forecasting at least as far ahead as the business's cash-flow cycle because that cycle determines how long cash can remain outside the business after costs have already been incurred.

That is the bit generic reserve rules miss.

You may need £150,000 merely to fund profitable work that has already been sold.

That isn't necessarily your reserve.

It may simply be the working capital requirement created by your business model.

The growth trap

This is where things get particularly interesting.

A business can run out of cash because it is failing.

It can also run out of cash because it is growing too quickly.

Imagine a manufacturing company wins a huge increase in orders.

Brilliant.

Revenue is rising.

Profit forecasts look fantastic.

Everybody celebrates.

Unfortunately, the business now needs to:

• Buy more raw materials
• Carry more stock
• Recruit additional employees
• Pay overtime
• Increase delivery capacity
• Fund larger customer credit balances

All before receiving some of the additional sales revenue.

The British Business Bank specifically warns that growth can increase cash-flow pressure because each additional sale may need working capital to fund stock, production or customer credit before the associated cash arrives.

This is why:

“We're profitable, so cash is fine.”

is one of the more dangerous sentences in business.

Profit and liquidity are related.

They are not interchangeable.

The four things I would build into a cash-reserve calculation

Rather than automatically choosing three months or six months, I would break the target into four parts.

1. Normal operating requirement

How much cash does the business need to trade normally?

This includes the timing difference between paying costs and receiving customer money.

2. Known liabilities

What significant cash requirements are already approaching?

For example:

• VAT
• Corporation tax
• PAYE and payroll liabilities
• Annual insurance premiums
• Loan repayments
• Equipment payments
• Supplier settlements
• Bonuses
• Renewals
• Deposits
• Planned capital expenditure

Do not call money an emergency reserve if HMRC already has a perfectly legitimate claim on a chunk of it.

For tax liabilities in particular, work with your accountant on the actual amounts due rather than relying on crude percentages.

3. Shock reserve

Now calculate the genuine buffer.

How many months of essential costs would you want available if revenue suddenly deteriorated?

This is where the usual two, three or six-month discussion becomes useful.

But only now.

4. Specific risk allowances

Does your business contain an unusually large identifiable risk?

Perhaps:

• One customer represents 40 per cent of revenue.
• Your biggest contract renews annually.
• December and January are routinely awful.
• A vital machine could require expensive replacement.
• Stock must be purchased months before peak season.
• You regularly suffer 60 to 90-day debtor periods.
• Your work depends on one licence or accreditation.
• A substantial legal or contractual exposure exists.
• You are about to recruit heavily.
• You are opening another location.

Those risks may justify additional headroom beyond your basic operating buffer.

A simple reserve formula

You could therefore think about your reserve target as:

**Essential operating runway

• cash-flow-cycle requirement
• known near-term liabilities
• specific contingency allowance**

Be careful not to double-count.

Some working-capital requirements will already appear inside your monthly cash forecast.

The objective is not to build the largest possible number.

It is to understand the cash that genuinely needs to be available.

So is three months enough?

Sometimes.

Let's take a relatively resilient business.

It has:

• Recurring monthly revenue
• Low customer concentration
• Healthy margins
• Few employees
• Low fixed overhead
• Little stock
• Short payment terms
• Predictable monthly expenditure
• Reliable cash forecasting
• Access to undrawn finance if genuinely required

That company may decide that holding six months of operating costs as idle cash is unnecessarily conservative.

Now consider another company.

It has:

• Heavy payroll
• Significant premises costs
• Seasonal revenue
• Four customers generating 70 per cent of sales
• 60-day payment terms
• High stock requirements
• Expensive machinery
• Limited access to additional borrowing
• Revenue that can move sharply month to month

Three months suddenly feels rather less generous.

The useful question is not:

“How many months should every business keep?”

It is:

“How quickly could this business get into trouble, and how long would it realistically take us to respond?”

Six questions that should change your reserve target

1. How predictable is your revenue?

Recurring contracted income gives you greater visibility than one-off project work.

That doesn't mean recurring revenue is guaranteed forever.

But predictability matters.

The more volatile your income, the more valuable financial headroom becomes.

2. How concentrated are your customers?

Losing one customer that represents 3 per cent of revenue is inconvenient.

Losing one representing 35 per cent can change the company overnight.

If customer concentration is high, model what happens if your largest account disappears.

Not because you expect it to.

Because it can.

3. How quickly can you reduce costs?

Some businesses are remarkably flexible.

Others aren't.

A consultancy using mainly associates may be able to reduce variable expenditure quickly.

A manufacturer with a large permanent workforce, leased premises, machinery finance and stock commitments has considerably less room to manoeuvre.

Your reserve needs to reflect the speed at which costs can realistically fall.

4. How long do customers take to pay?

Late payment can destroy an otherwise sensible reserve calculation.

The Small Business Commissioner recommends agreeing payment terms clearly in advance, invoicing promptly and acting quickly when invoices become overdue. Its guidance also highlights deposits and staged payments as possible ways of reducing exposure on larger work.

If your customers routinely pay late, do not build your cash forecast around contractual payment terms that nobody actually observes.

Use reality.

If invoices say 30 days but the average customer pays in 52, model 52.

5. How seasonal is the business?

A hotel in a seasonal tourist location does not experience cash in the same way as a subscription software business.

Neither does a landscaping company.

Or a Christmas retailer.

Or a business heavily exposed to school holidays.

Your reserve needs to survive your normal trough before it even starts protecting you from abnormal events.

6. How easily could you access additional finance?

Available finance can provide useful headroom.

But be very careful about treating future borrowing as though it were cash already sitting in the bank.

The best time to obtain finance is rarely the week after the business becomes desperate for it.

British Business Bank guidance recommends dealing with anticipated working-capital shortfalls before they actually hit and discusses options including overdrafts, invoice finance and other forms of working-capital funding.

Current Bank of England intelligence also shows why owners should not assume borrowing will always be equally available. In September 2026, its Agents reported strong lender competition for viable borrowers but noted less appetite for some smaller firms and companies with weaker trading records.

Finance is a tool.

It isn't a substitute for resilience.

Stress-test the reserve rather than arguing about the number

This is considerably more useful than debating whether three months sounds sensible.

Take your current cash position and run scenarios.

Scenario 1: Largest customer disappears

What happens?

When does cash become uncomfortable?

When does it become critical?

Scenario 2: Revenue falls 25 per cent for three months

Can you continue operating normally?

What expenditure would need to change?

Scenario 3: Customers pay 30 days later

How much extra working capital disappears?

Scenario 4: One major unexpected cost hits

A £50,000 machine repair.

A legal bill.

A major bad debt.

A stock write-off.

Whatever is credible for your company.

Scenario 5: Growth jumps 30 per cent

Yes, stress-test growth too.

How much additional stock, payroll, materials or credit do you need to fund before customers pay?

A good reserve policy should survive credible scenarios.

It doesn't need to survive the end of civilisation.

Cash reserves buy time

This is the bit that gets overlooked when people reduce everything to finance ratios.

Cash buys decision-making time.

If the business has ten days of money left, every decision becomes desperate.

You take work you shouldn't take.

Accept prices you shouldn't accept.

Keep customers you should probably lose.

Cancel investment that should continue.

Borrow on poor terms.

Make panicked staffing decisions.

Chase every possible sale regardless of margin.

The shorter the runway, the fewer choices you have.

Cash reserves create space between:

Something has gone wrong

and:

We have to do something stupid immediately.

That space has enormous commercial value.

Too little cash creates risk

This is obvious.

Payroll arrives whether or not your customer has paid you.

So does rent.

HMRC.

Finance.

Suppliers.

One large delayed payment can create enormous stress when there is no buffer.

The Office for National Statistics continues to ask UK businesses how long their cash reserves would last, using bands of less than one month, one to three months, four to six months and more than six months. That doesn't prescribe the correct reserve, but it reflects how useful cash runway is as a measure of business resilience.

Recent conditions also demonstrate why resilience remains relevant. In the ONS Business Insights and Conditions Survey published on 24 September 2026, 28 per cent of trading businesses reported lower turnover in August than July, while economic uncertainty remained the most commonly reported turnover challenge. The ONS notes that these estimates are subject to sampling and other uncertainty.

Unexpected months happen.

The reserve determines whether an unexpected month becomes an existential problem.

But too much cash can also be a problem

This is the other side of the conversation.

I've met owners who become almost addicted to accumulating cash.

The number becomes emotional security.

£100,000 becomes £200,000.

Then £300,000.

Then nobody is quite sure what the money is actually for.

Meanwhile:

• Equipment needs replacing.
• Marketing opportunities are ignored.
• Good people aren't recruited.
• Expensive debt continues.
• Systems remain outdated.
• The owner refuses to invest in capacity.

Cash exists to protect and enable the business.

Not merely to produce a comforting number on a banking app.

Once you have identified the amount required for:

• Normal working capital
• Known liabilities
• Sensible resilience
• Planned investment

then anything materially beyond that deserves a separate conversation.

What should happen to excess cash will depend on the company, its debts, tax position, investment plans, ownership structure and the directors' objectives.

That is where your accountant and, where appropriate, authorised financial advisers become useful.

I wouldn't make that decision based on a generic internet article.

Including this one.

Separate the money mentally and, where useful, physically

One reason business cash gets accidentally spent is because everything sits in one account.

The balance says:

£240,000

which psychologically feels available.

But perhaps:

• £45,000 relates to upcoming tax.
• £60,000 is the operating buffer.
• £75,000 funds committed projects.
• £40,000 is genuine reserve.
• £20,000 is genuinely unallocated.

You don't necessarily need five bank accounts.

But you do need visibility.

Some businesses find separate accounts useful for things such as:

• Tax
• Operating cash
• Reserve cash

The exact structure is for you and your accountant to determine.

The principle is simply that money with a future job should not be mistaken for surplus cash.

Where should a business keep its cash reserve?

A reserve only works if the money is accessible when it is needed.

That does not necessarily mean every pound needs to sit in a zero-interest current account.

But accessibility, security and the timing of withdrawals matter.

If using business savings or deposit accounts, understand:

• How quickly money can be accessed
• Whether withdrawals are restricted
• Whether notice is required
• What interest is paid
• Who legally holds the deposit
• Which banking licence the institution operates under
• What deposit protection applies

For UK businesses, the Financial Services Compensation Scheme deposit limit increased to £120,000 on 1 December 2025. Most eligible limited companies and LLPs are treated as separate legal entities and can receive up to £120,000 of deposit protection per authorised banking firm. For sole traders, personal and business deposits with the same authorised institution are aggregated because the business is not legally separate from the individual. Banks within the same group may also share one banking licence, so multiple brands do not necessarily create multiple protection limits.

That becomes relevant once your reserve grows into meaningful six-figure territory.

This is not investment advice.

It is simply another risk to understand rather than assuming cash is automatically risk-free because it is sitting in a bank account.

Build the reserve gradually

Suppose your calculation suggests the business should hold £180,000 of genuine reserve.

Today you have £55,000.

That doesn't mean you need to somehow find £125,000 next Tuesday.

Turn it into a target.

For example:

Current reserve: £55,000
Target reserve: £180,000
Gap: £125,000

Then decide how the business will close it.

Possibilities might include retaining a defined proportion of monthly profit, improving debtor collection, changing payment structures, improving margin or temporarily moderating discretionary expenditure.

The method will depend on the business.

Track the reserve just like any other important business objective.

If you don't deliberately build it, there is a decent chance any surplus will simply disappear into general expenditure.

Don't build reserves while ignoring broken cash management

This matters.

A business shouldn't need a gigantic reserve simply because its financial processes are terrible.

If customers routinely owe you £400,000 because nobody chases debt, fix credit control.

If stock worth £250,000 hasn't moved in two years, address stock management.

If every customer receives 90-day terms for no commercial reason, reconsider the terms.

If invoices routinely go out three weeks late, fix invoicing.

If jobs are consistently underpriced, fix pricing.

The Small Business Commissioner emphasises basics including agreeing payment terms, invoicing promptly, understanding customers' payment processes and following up overdue debt.

Cash reserves should protect you from uncertainty.

They shouldn't subsidise poor management indefinitely.

Recalculate the target as the business changes

Your ideal reserve at £500,000 turnover is unlikely to remain correct when the company reaches £3 million.

Headcount changes.

Premises change.

Customer concentration changes.

Debt changes.

Margins change.

Payment terms change.

The sales mix changes.

You may acquire another company.

Open another location.

Buy machinery.

Introduce recurring revenue.

Lose recurring revenue.

The reserve target should move with the company.

Review it at least as part of your normal financial planning and whenever there is a substantial change in the business.

A cash-flow forecast is especially valuable here because it shows when money is expected to enter and leave rather than relying on the current bank balance. The British Business Bank recommends regularly updating forecasts as better information becomes available and stresses that forecasts should cover at least the business's cash-flow cycle.

A simple cash-reserve review for business owners

If I were sitting with an owner trying to establish whether their reserve was sensible, I would work through this sequence.

Step 1: Find your essential monthly outgoings

Not total spend.

The money the business cannot quickly stop spending.

Step 2: Map the cash-flow cycle

When do you spend money?

When do customers actually pay?

How much cash normally gets trapped between the two?

Step 3: Ring-fence known liabilities

Tax.

Payroll.

Suppliers.

Finance.

Committed capital expenditure.

Anything already spoken for.

Step 4: Measure your commercial risk

How volatile is revenue?

How concentrated are customers?

How seasonal is the company?

How fixed is the cost base?

Step 5: Choose a sensible operating runway

Test two months.

Three months.

Four months.

Six.

See what each actually means in pounds.

Step 6: Stress-test it

Lose the biggest customer.

Delay debtors.

Reduce revenue.

Increase costs.

Model rapid growth.

Where does the business become uncomfortable?

Step 7: Decide the reserve target

Not because somebody told you every business needs £250,000.

Because you can explain exactly why your business needs the amount you selected.

That last part matters.

You should be able to say:

“Our reserve target is £220,000 because that gives us approximately three months of unavoidable operating expenditure, allows for our payment cycle and gives us additional protection against our largest customer concentration.”

That is management.

“We keep £220,000 because it feels about right.”

isn't.

The reserve is there to preserve agency

There is another reason I care about this beyond accountancy.

Agency disappears very quickly when you run out of options.

When the bank account is empty, customers dictate terms.

Lenders dictate terms.

Suppliers dictate terms.

Urgency dictates terms.

You stop asking:

What is the best decision?

and start asking:

What can we do before Friday?

A sensible reserve gives the owner room to think.

Room to reject bad work.

Room to deal with a lost customer.

Room to make a redundancy decision properly rather than impulsively.

Room to survive a delayed payment.

Room to invest when an opportunity appears.

Room to fix the actual problem instead of desperately treating symptoms.

Cash is not the point of owning a business.

But running out of it has a remarkable ability to make cash the only thing you can think about.

So, how much cash should you keep?

Start with essential cash outgoings, not turnover.

For many established small businesses, modelling what two to three months of unavoidable operating expenditure would look like is a sensible first exercise.

Then adjust.

Hold more if your business has:

• Volatile revenue
• High fixed costs
• Heavy payroll
• Long payment cycles
• Significant seasonality
• High customer concentration
• Large stock requirements
• Limited access to finance
• Material operational risks

You may reasonably need less if revenue is highly predictable, costs are flexible, customers are diversified, cash conversion is rapid and additional funding is genuinely accessible.

Then add known liabilities and genuine working-capital requirements.

Stress-test the result.

Review it regularly.

And make sure the number is based on what your company actually needs rather than an arbitrary rule somebody copied from somebody else.

The objective is not to hoard cash.

The objective is to make sure a difficult month remains a management problem rather than becoming a survival problem.