How it’s worked out
When you work through an umbrella company, the agency pays your full assignment rate to the umbrella. The umbrella takes its margin, then pays employer National Insurance (15% on salary above £5,000) and the 0.5% apprenticeship levy. What's left is your gross salary, which is taxed through PAYE like any job.
Because employer NI and the levy depend on your salary, the calculator solves for the salary that uses up exactly what's left after the margin. That's why the employer costs look large: they come out of your rate rather than on top of it.
Paying into a pension by salary sacrifice reduces your gross salary before income tax and employee National Insurance, so every £100 into your pension costs you less than £100 in take-home pay. This calculator keeps employer NI on the full salary, which is how most umbrellas work; some pass on the employer NI saving too, which would leave you slightly better off.
Ask any umbrella for a Key Information Document before you sign. It must show the margin and every deduction, so you can check it against these figures.
Questions
What is a typical umbrella margin?
Usually £15 to £30 a week, or a monthly fee. Very low margins can be a warning sign, so check for accreditation from the FCSA or Professional Passport.
Why is my umbrella take-home lower than a limited company?
Employer NI, the apprenticeship levy and the margin come out of your rate, and all of your pay is taxed as salary rather than dividends.
Does a salary-sacrifice pension save tax?
Yes. It reduces both income tax and employee National Insurance on the amount you put in.
These figures are estimates for guidance only and aren’t financial or tax advice. Speak to an accountant before making decisions.