The tax cliff this scenario is closest to
Before the numbers, a warning: a mobile mechanic at £55,000 of turnover for 2026/27 is sitting close to one of the UK tax code's sharpest cliffs.
The £50,270 higher-rate threshold and the £12,570 Personal Allowance are the two boundary numbers a sole trader at this turnover needs to watch. Each £1 of profit above £50,270 attracts the 40% income tax rate plus the 2% Class 4 NI rate — a combined 42% marginal — versus the 28% basic-rate + main-band combination below. Most "should I incorporate?" questions are actually triggered by a sole trader crossing the £50,270 boundary, because the dividend-band machinery starts paying for itself there.
The numbers for this specific scenario
Bottom line for a mobile mechanic at £55,000 of turnover: net cash £41,437; pension £0; effective rate on gross 19.7%.