Primary employment. Job 1 fully uses your tax-free Personal Allowance and the lowest tax bands first. Every job after this one is calculated as additional income stacked on top, taxed through the next available bands — equivalent to HMRC's BR (20%), D0 (40%) or D1 (45%) secondary tax codes.
PAYE salary
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£
£
£
£
£
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Tax fee income as self-employment: Class 4 NI + income tax on profit, no Corp Tax/dividends. Assumes not VAT-registered.