The danger of one big customer
Spot when one customer has too much of your business, and spread the risk before it bites.
5 min read
Landing a big customer feels like the business has arrived. Steady orders, a known name, less time spent hunting for sales. But when one customer becomes most of your business, they also become your biggest risk. If they leave, pay late or squeeze your price, there is nothing else to fall back on — and they usually know it.
How it goes wrong
The pattern is common enough to recognise early:
- A big customer starts ordering. You take on staff, stock or machines to serve them.
- They become a larger and larger share of your sales. Other customers get less attention.
- They ask for a lower price, longer credit or extra work for free. Saying no feels impossible.
- They change supplier, cut their order, or run into trouble themselves — and your business has to shrink overnight, with costs built for a bigger one.
It happens to good businesses with good customers. The customer does not have to behave badly; their own plans just have to change.
Measure your exposure
Once a quarter, list your customers by how much they bought. Then look at what share of your sales the top one, and the top three, make up.
| Share of sales from your biggest customer | What it means |
|---|---|
| A small part | Healthy. Losing them hurts, but you survive. |
| A large part | Watch it. Start actively building others. |
| Most of it | You depend on them. Make spreading the risk a priority. |
There is no single right number — it depends on your business and how secure the relationship is. What matters is knowing the share, and noticing when it climbs.
Look at profit too, not just sales. A big customer who negotiated a thin price and long credit can bring a large share of your sales but a small share of your profit — and most of your working-capital strain.
Reduce the risk
- Keep selling to others even when the big customer keeps you busy. Set aside time every week for new enquiries.
- Find customers in a different industry or area. If all your customers are in one trade, they will all slow down at once.
- Do not build all your costs around them. Be careful about long-term rent, loans or permanent staff that only make sense with their orders.
- Watch how they pay. Payments getting slower is often the first sign of a problem. Keep their credit limit firm — see checking a new customer.
- Put the terms in writing. Agreed prices, payment terms and notice before they stop ordering — see put it in writing.
Do not accept terms from a big customer that you would refuse from anyone else — a price below your cost, credit you cannot fund, or exclusivity that stops you selling elsewhere — just because they are big. A customer who only pays when you lose money is not a customer, it is a cost.
Use the big customer well
A large customer is still valuable. Use the relationship to make the business stronger:
- Ask for a reference you can show to other buyers.
- Use the steady orders to improve your processes and quality.
- Build up savings while the orders are good, so a loss of business is survivable.
- Agree prices that leave you a proper margin — your reliability is worth paying for.
If you are already dependent
Do not panic, and do not drop them. Make a simple plan: a target for how much of next year's sales should come from other customers, and the specific steps to get there — new products, new areas, new kinds of buyer. Review it every quarter, alongside your monthly review.
Describe your customers and what each buys to the tool below, and it will help you see how exposed you are and where new customers might come from.