How is the required day rate found?

The calculator uses a safe binary search over possible day rates until the inside IR35 take-home pay meets the target.

Can I match a permanent salary?

Yes. Choose the permanent salary mode and enter the gross salary you want the contract to match after estimated deductions.

IR35 Day Rate Calculator - Required Inside IR35 Rate

How to use this IR35 day rate calculator

Choose whether you want to target an annual take-home amount, match an outside IR35 day rate, or match a permanent salary. Enter the target and working pattern, then review the required inside IR35 rate.

Methodology and formula

The calculation uses an iterative binary search. Each trial day rate is passed through the inside IR35 calculator until the estimated take-home reaches the target.

while estimated_take_home differs from target:
    try midpoint_day_rate
    move the search range up or down

Example calculation

To target £75,000 annual take-home over 230 working days, the solver tests day rates until the inside IR35 PAYE result reaches that annual target.

Important considerations

The required uplift depends heavily on umbrella margin, employment cost treatment, pension, tax code, and unpaid time. A client may quote assignment rate, gross taxable pay, or another rate basis.

FAQ

Why use a solver instead of a simple multiplier?

UK tax, NI, allowances, employer costs, and pension assumptions are not linear, so a fixed multiplier can mislead at higher incomes.

Can the result be too high for the market?

Yes. This is a financial target calculator, not a market-rate benchmark.

Disclaimer

Results are estimates and are not tax, financial, legal, employment, or negotiation advice. Verify assumptions before relying on a rate target.