How many days is your business from trouble?

It is a Tuesday morning. You are going through email with a coffee, and there is one from your largest client. The subject line is neutral — "quick update" — so you open it without any sense of what is coming.

They are restructuring. Budgets are being consolidated. They have valued the work enormously and will of course provide a reference. The contract ends in thirty days.

You read it twice. Then you do the arithmetic you have been avoiding for about two years, and discover that this one client was something like 40% of your income, and that you have no idea how long you can operate without them.

That morning arrives for a great many small businesses, and the people it arrives for are rarely the ones who were careless. They were busy. The client was reliable right up until the moment they were not, and nothing about the relationship signalled otherwise — which is precisely why the email is a shock rather than a development.

The useful question is not how to prevent that email. You cannot. It is how many days you have after it lands, and whether you know the number before you need it.

Most businesses have far less time than they think

The conventional advice is to hold three to six months of operating expenses in reserve. It is repeated so consistently that most owners assume businesses broadly manage it, and that falling short makes them an exception.

They do not, and it does not.

The JPMorgan Chase Institute examined roughly 597,000 small businesses and more than 470 million transactions, and measured what it called cash buffer days — how many days a business could keep covering its normal outgoings from existing balances if every inflow stopped. The median was 27 days.

Not three months. Under four weeks.

The figure varies considerably by industry:

It also splits by cost structure. Labour-intensive businesses held a median of 23 days; capital-intensive businesses, 38.

One important caveat, and it matters: this was the Institute's inaugural small business report, and its data is from 2016. It remains the largest study of its kind and the most widely cited, but it describes small business cash positions as they were a decade ago, not as they are today. Treat the 27 days as an indication of how thin buffers typically are rather than a current measurement. The point it makes — that the gap between the three-month rule and actual practice is enormous — has not been seriously challenged since.

What the number tells you is that if your own buffer is three weeks, you are not failing at something other businesses have solved. You are in the middle of the distribution. That is worth knowing, because owners who believe they are uniquely bad at this tend not to look at it at all.

Work out your own number

It is a short calculation and you can do it today.

Take your business bank balance — only money you could actually spend, so exclude anything already committed to tax. Divide it by your average daily outgoings: your monthly fixed costs plus typical variable spend, divided by thirty.

The result is your buffer days. It is the number of days you could continue operating if every payment stopped arriving tomorrow.

Do it honestly. The most common error is leaving out the money that is not technically a business cost but still has to be paid — your own drawings, the mortgage, the things that do not stop because revenue did. If the business is your only income, those belong in the calculation.

Most people doing this for the first time find the number is somewhere between two and five weeks, and find it sobering. That reaction is the useful part.

The concentration test

The second number is about where your income comes from rather than how much you hold.

Work out what share of your revenue comes from your single largest client. Then your largest two.

There is no universal threshold, but the practical reality is straightforward: when one client is 40% of revenue, you are not running a business with a large client. You are employed by them, without any of the protections employment carries. No notice period, no redundancy entitlement, no unemployment claim. The contract ends when they say it does.

This is written about fairly often, but almost always from the perspective of selling a company — buyers discount a business with concentrated revenue, which is true and irrelevant to most people reading this. The version that matters when you are not selling is simpler: concentration determines how much of your income can disappear in a single email.

Note that concentration and buffer multiply rather than add. Twenty buffer days with evenly spread clients is uncomfortable. Twenty buffer days with one client at half your revenue is a different category of problem, because the event that empties your pipeline and the event that drains your reserves are the same event.

What a 20% drop actually does

Here is where intuition fails most reliably.

Lose 20% of your income and the instinct is that you need 20% more work to recover. You need 25% — the shortfall is measured against the smaller base you are left with. At a 30% drop it is roughly 43%. And replacement clients arrive with their own costs: pitching time, onboarding, admin, the unpaid weeks before the first invoice clears.

This is the arithmetic that decides whether a bad quarter is survivable or terminal, and it is almost never done in advance.

The Business Resilience Check runs the scenarios for you. Enter your current revenue and costs, and it models what happens at income drops of 10, 15, 20 and 30% — including your break-even point and how many clients you need at each level to hold your position. If the answer at 20% is more clients than you could physically service, you have learned something important about how much cushion you actually need, and you learned it on a quiet afternoon rather than during the thirty days' notice.

Three things that actually buy resilience

Saving more is the obvious answer and the least available one. If there were spare money it would already be saved. More useful, in rough order of effect:

Shorten your payment terms. Buffer days are a function of timing as much as amount. Moving from 30-day to 14-day terms on new contracts, invoicing on completion rather than month end, and taking a deposit on larger projects all raise your balance without raising your revenue. This is the fastest lever available to most small businesses and the most consistently ignored.

Know your floor. You cannot judge whether a client is worth keeping at a reduced rate unless you know the rate below which the work costs you money. The Freelance Day Rate Calculator establishes that floor from your target income, real costs and genuinely billable days. Related: what to charge when AI makes you faster covers how to price when your delivery time has collapsed but your value has not.

Keep a pipeline when you do not need one. The best time to talk to prospective clients is when you are busy, because you negotiate from a different position and you are not visibly desperate. A pipeline built during good months is the only thing that shortens the gap after a bad email. If you are still establishing a baseline, how many clients you need to go full-time freelance covers that arithmetic.

What to do this week

Three numbers, twenty minutes.

Calculate your buffer days. Spendable balance divided by daily outgoings.

Calculate your largest client's share of revenue. Then your largest two.

Run a 20% drop through the resilience check and read what it says about client numbers.

You may find all three are fine, in which case you have spent twenty minutes buying certainty. More likely one of them is worse than you assumed. Either way you will know the number, and knowing it is what separates a difficult quarter from the Tuesday morning where the arithmetic happens for the first time while you are reading an email.