Client Dependency Calculator
How exposed are you to losing one client?
Use a typical recent month rather than your best one — three-month averages work best. Every field has guidance and an example figure, and everything is calculated in your browser: nothing is stored or sent anywhere.
Hayley Duster — writer and solo business owner
Total invoiced income in a typical month, before tax and before costs.
Example: £18,000 invoiced over three months = £6,000 a month
The single client contributing most. Count a retainer at its monthly value.
Example: £3,000 monthly retainer
Used only to show how much of your income two relationships control.
Example: £1,200 of project work each month
Business costs you cannot switch off plus the minimum you must draw personally. Exclude discretionary spending.
Example: £900 business + £2,600 personal = £3,500
Cash you could genuinely spend. Do not include money owed to the tax authority, client deposits or credit facilities.
Example: £4,000 in a separate savings account
High concentration risk — One client decision would remove most of your income. Reducing this is usually the highest-value change available to you. Read this as: for every £100 you invoice, £50 depends on one relationship.
Above 60% here means two conversations control your year. Below 40% is a comfortable spread for a solo business.
Assumes every other client keeps spending exactly as they do today.
This is the gap you would need to close through reserves, new work or reduced costs.
Reserves divided by the monthly shortfall. Most replacement work takes two to four months to win and start invoicing, so under 3 months here is the warning line.
How this is calculated (version 1.1, reviewed 24 August 2026)
- Figures are monthly and exclude VAT or sales tax; the calculator does not model payment delays or late invoices.
- Losing your largest client is treated as an immediate, total stop — in reality a notice period usually gives you one to three months.
- Remaining clients are assumed to spend the same amount, with no work won or lost in the meantime.
- Reserves are treated as fully available cash; tax set-asides and client deposits are not yours to spend.
- Months of cover measures only the gap between remaining income and essential costs, not your full cost base.
- The risk bands use an editorial threshold: 30% marks elevated concentration and 50% marks high concentration. This is a planning heuristic, not a legal, tax or financial rule.
- All calculations stay in this browser; this page does not send the numbers you enter to analytics.
A worked example
A designer invoices £6,000 a month. Her largest client pays a £3,000 retainer, her second pays £1,200, essential costs are £3,500 and she holds £4,000 in reserve.
- Largest client share
- £3,000 ÷ £6,000 = 50%
- Revenue left if they leave
- £3,000 a month
- Shortfall against essentials
- £3,500 − £3,000 = £500
- Cover from reserves
- £4,000 ÷ £500 = 8 months
Her concentration is high at 50%, but because her costs are close to her remaining income the shortfall is small and her reserves stretch a long way. The action is pipeline work, not panic — she has roughly two quarters to replace the retainer.
What to do with this
- If your largest client is above 30%, treat pipeline work as a standing weekly task rather than something you do when work dries up.
- Check the contract: notice period, payment terms and whether work can be paused without warning. Notice length is your real planning window.
- Aim for reserves that cover the shortfall for at least three months while you replace the work.
This organises your own numbers and is not financial advice. Speak to a qualified accountant about decisions specific to your business.
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