£10,000 is the most-searched lump sum in UK personal finance, and it usually represents one of three things: a year-end work bonus, an inheritance from a grandparent, or several years of disciplined saving. In each case the strategic question is the same — wrapper sequencing. Where the money sits matters almost as much as what you invest in.

First priority: your £20,000 annual ISA allowance (use-it-or-lose-it at 5 April). £10,000 fits comfortably inside it. A Stocks and Shares ISA with VWRP (Vanguard FTSE All-World Acc, 0.22% OCF) or the cheaper HSBC All-World Index (0.13% OCF) gives you global equity exposure with dividends compounding tax-free. If you're near the 5 April deadline and haven't used this year's allowance, this is the most time-sensitive financial decision you'll face all year.

Second question: SIPP or mortgage overpayment with any remaining amount? For 40% taxpayers, SIPP contributions carry an effective 67% instant uplift — at current 2yr fixed mortgage rates of ~4.1% this decisively wins. For basic-rate taxpayers, the SIPP advantage shrinks to 25% uplift, and overpaying a mortgage above 4.5% becomes increasingly competitive. Most lenders cap penalty-free overpayment at 10% of outstanding balance per year.