Some clients are a whale on the top line. And a mouse on the bottom.

Most business owners have had one. The big client. The one that brings in a big chunk of revenue.

And a constant source of stress.

They pay well, but they drain you. You tolerate them because, well, look at the invoice.

My first question is always the same. What percentage of your revenue are they? Then, what percentage of your profit?

They're rarely the same number.

There's the hard cost. That's the wages of the people who look after them. Then there's the invisible cost. The hours you and your managers spend stepping in and managing it.

You might not be the one making the phone calls. It's still your time. If you're worrying about it, it's costing you.

So cost it. Estimate everyone's hours on this client this week. Add them to the wages. Then look at what the profit really is.

It can be a whale on the top line. And a mouse on the bottom.

Then ask one more question. Knowing what you know now, would you take them on again?

If the answer is no, start working out how and when.