Engineering contractor on £99,000

Inside-IR35 Umbrella. Inside IR35. Age 34. Pension preference: modest.

Every figure on this page is computed at build time by the same engines that power the live salary–dividend split, take-home and SIPP optimiser calculators. Inputs come from a single CSV row; outputs come from the engines. No static lookup tables, no hand-coded numbers.

Net cash

£56,620

Pension

£4,950

Effective rate

37.8%

Marginal rate

42%

Step by step: how the engine arrived at the bottom line

The inside-IR35 engine ran the umbrella-deduction stack in the same order an umbrella company actually pays the money out. Here are the steps that produced the bottom line for a engineering contractor on a £450/day inside-IR35 contract (220 days assumed):

Contract value: £99,000 (day rate × 220 days).
Umbrella fee: £1,500 deducted off the top.
Salary sacrifice (pension): £4,950 taken off pre-tax / pre-NI as a salary sacrifice — by far the most efficient lever inside IR35.
Employer NI: £13,133 on what remains (15% above the £5,000 Secondary Threshold).
Gross deemed salary: the remainder is paid as a salary subject to PAYE.
Income tax: £19,199 at 20% / 40% / 45% on the deemed salary.
Employee NI: £3,599 at 8% main band, 2% above £50,270.
Net cash: £56,620. Net wealth incl. pension: £61,570.

Break-even day rate to match the outside-IR35 equivalent: £504/day.

The numbers, line by line

Day rate	£450
Contract value (220 days)	£99,000
Inside-IR35 net cash	£56,620
Inside-IR35 pension	£4,950
Outside-IR35 net cash	£62,161
Outside-IR35 pension	£4,500
Cost of being inside IR35 (net wealth)	£5,091
Break-even outside-IR35 day rate	£504

Why this scenario is different

Compared to the closest peer profile — Software contractor at £88,000 — this scenario sits £11,000 higher on gross income. That moves net cash by +£5,152, the pension contribution by +£550, and the effective rate by +1.3%. The effective rate moves only modestly — both scenarios sit inside the same binding tax band. The break-even outside-IR35 day rate moves from £454 to £504 per day.

Questions this scenario raises

Is the figure on this page net of accountancy fees?

Yes when relevant — the take-home calculator deducts an umbrella fee for inside-IR35 rows (£1,500/yr assumed) and the optimiser allows for an arbitrary annual business expense pot (£3,500/yr default for Ltd Co rows). Sole-trader rows assume the higher of £800/yr or 5% of turnover as actual business expenses, which approximates a low-overhead service business.

Where does the BracketMath engine source its rates?

Income tax / NI / CT / dividend rates come from HMRC's published 2026/27 rate tables (gov.uk/government/publications/rates-and-allowances-income-tax). Pension rules come from FA 2004 and the FCA's consumer guidance. Historical investment returns used in the Monte Carlo engine come from a 125-year UK gilt + UK equity series stored in src/data/historical-returns.json. Every constant carries a source URL in the source code.

Does this calculation include student loan repayments?

No. Student Loan repayments (Plan 1 / 2 / 4 / 5 / Postgraduate) are not modelled in the BracketMath engines. Plan 2 repayments at 9% above £27,295 add roughly 9p of marginal cost to each £1 of taxable income above the threshold. Add this to the marginal rate quoted on this page if you have an outstanding student loan.

What happens to my pension at age 55 / 57?

From age 55 (rising to 57 from 6 April 2028 per the Finance Act 2021) you can access defined-contribution pensions. The first 25% of the pot is tax-free (the "Pension Commencement Lump Sum"), subject to the £268,275 Lump Sum Allowance. The remainder is drawable at your marginal income-tax rate — but you can phase it across decumulation years to keep most of it within the 20% basic-rate band.

What is the cost of being inside IR35 vs outside at this day rate?

For this row, operating inside IR35 instead of outside costs £5,091 per year of net wealth (cash + pension). To match the outside-IR35 take-home at the same day rate, an inside contract would need to be priced at approximately £504/day.

Methodology

Income tax, National Insurance and Corporation Tax bands taken from HMRC's 2026/27 rates and allowances tables (gov.uk/.../income-tax; corporation-tax). Pension Annual Allowance and taper rules from Finance Act 2004 / 2023. Trading allowance per ITTOIA 2005 s.783A. Voluntary Class 2 figure (£179.40/yr = £3.45/wk × 52) from HMRC voluntary NI guidance.

Style: 2026/27 tax year throughout; figures rounded to whole pounds in the user-facing prose; effective rates computed as (deductions / gross). The voice is methodological — no first person, no claimed credentials, no marketing fluff.

This page is not personalised advice; for advice regulated by the FCA, consult an adviser registered with the Financial Conduct Authority. See the full disclaimer.