UK side hustles surge, with 40% of Brits earning side income, prompting tax deadline warnings and free tool launch.

A surge in UK side hustles, driven by platforms like Vinted and the "Thriftmas" trend, has led to a 50% rise in related Google searches, with many earners exceeding the £1,000 self-employment threshold requiring HMRC registration and tax filing. Nearly 40% of Brits now have side incomes averaging nearly £11,000, risking penalties if they miss the January 31, 2026, tax deadline. To help, GoSimpleTax launched a free calculator estimating take-home pay after taxes and expenses.