IR35 calculator UK: inside and outside on the same rate

What this inside vs outside IR35 calculator does, step by step

1. Start with the rate and say what it is. Enter your day or hourly rate and state whether it is the assignment rate the client pays or the gross you expect. On an inside engagement through an umbrella, the assignment rate funds employer National Insurance, the Apprenticeship Levy where it applies, holiday and the umbrella margin before your gross pay exists.
2. Set the billable time honestly. Annualising a day rate by 260 days assumes no holiday, no illness and no gap between contracts. Use the weeks you actually expect to bill: it is the single input that moves the annual figure most, and it is the one every optimistic comparison quietly gets wrong.
3. Inside: run employment deductions. For the inside position the model applies the current allowance, Income Tax bands and employee National Insurance to the gross, as a deemed employer would. It then shows the student loan separately, because GOV.UK states deemed employers do not deduct student or postgraduate loan repayments from an off-payroll worker's fees.
4. Outside: run the company route. For the outside position the fee is company income: corporation tax applies to profit, and what you keep depends on the salary and dividend split and on any company pension contribution. The model shows the split it assumed, because a headline outside figure with a hidden drawing plan is not a comparison.
5. Read the gap, not the winner. The output is two net figures and the reasons they differ, so you can see how much of the gap is employer National Insurance, how much is the umbrella margin, and how much is the drawing plan. A tool that prints one number and a recommendation has made your decisions for you.

Common questions

Which rate should I enter?

Whichever you have, and then say which it is. If a client or agency has quoted you an assignment rate for an inside engagement, that figure has employer costs and any umbrella margin to come out of it before your gross pay is set.

Why does an inside IR35 calculator show less than an employee's pay?

Mostly because the assignment rate carries employer National Insurance that an employee never sees, and because the student loan is paid separately through Self Assessment rather than deducted at source, so a deemed-employment payslip overstates what you keep.

Does an outside IR35 take home calculator include my accountant and insurance?

Only if you enter them as company costs. They are real and they belong in the comparison: accountancy, professional indemnity, and the unpaid weeks between contracts are what the outside route buys its higher net with.

Is this tax advice?

No. It applies published statutory rates to the figures you enter and shows its workings so you can check them. What it cannot do is decide your status or tell you which route to take, and any tool that offers to should be treated with suspicion.

Take-home pay by jurisdiction

• Take-home pay in United Kingdom