One big, dependable client is the most comfortable trap in freelancing. The invoices clear on time. The work is familiar. You stop chasing leads because you do not need to. Then the email arrives: a budget cut, a reorganisation, a new manager, and the client that paid most of your bills is gone by the end of the month.
That is the risk almost everyone sees, eventually. There is a second one sitting underneath it that hardly anyone talks about. When a single client provides most of your income and you do most of your work for them, tax authorities can start to treat you less like a business and more like that client's employee. The closeness that concentrates your income also puts your independent status in question. Both risks come from the same place, and you can defuse them with the same moves.
The number that should make you uncomfortable
There is a rough line where one client stops being a great account and starts being a liability. In corporate finance the warning marks are well defined. A single customer worth more than 10% of revenue, or your top five worth more than a quarter of it, counts as a concentration risk worth flagging (Wall Street Prep). US accounting rules bake that same 10% line into what public companies must disclose.
You are not a listed company, so your thresholds are looser. A workable rule of thumb for a one-person business: no single client should sit above roughly a third of your income, and once one pushes past 40%, treat it as a flashing light rather than a milestone. Most freelancers never run the number. They know the client is big. They do not know it was 60% of the year until the year is already over.
Risk one: the income can vanish in a single email
When a business dies, the headline cause is almost always the same. Of the venture-backed companies CB Insights studied, running out of cash or failing to raise more was the top reason for failure, cited in 70% of cases (). For a one-person business, running out of cash usually has a name, and it is the client who just walked.
