UK Side-Hustle Tax Set-Aside 2026/27 (Self Assessment tracker)

Got a job AND a side hustle? This spreadsheet works out the EXTRA income tax and Class 4 NI your side income adds on top of your PAYE salary, so you set aside the right amount, not too much. Includes the £1,000 trading allowance vs expenses comparison, 45p/25p mileage, personal allowance taper (£100k to £125,140), a Scotland option, payments on account warning, income, expense and mileage logs, and a 31 January checklist. 2026/27 rates checked against GOV.UK (sources inside). Estimate only, not tax advice. Excel, Google Sheets, LibreOffice. Try the free Lite version first: https://payhip.com/b/y6fwj . Made with the help of an AI assistant; tested against hand calculations before release.