Should I invest a lump sum all at once or spread it out?

Mathematically, investing it all at once wins more often than not — historically around two-thirds of the time — because markets rise more often than they fall, so time in the market beats waiting. But spreading it over a few months is a reasonable choice if it's the difference between investing and freezing. **Why lump sum wins on average**: money sitting in cash while you spread it in is money not earning returns. Since markets trend upward over long periods, delaying exposure has a cost. Studies across multiple markets and long time periods consistently find lump sum outperforms averaging-in most of the time. **Why averaging in is still defensible:** - **It reduces regret risk.** If you invest everything the week before a 30% fall, the psychological damage may cause you to sell — which is far more costly than the initial timing error. - **The average outcome hides the distribution.** Lump sum wins more often, but its worst outcomes are worse. If a bad outcome would genuinely derail you, paying a small expected-return cost for lower variance is rational. - **Behaviour beats optimisation.** A strategy you can follow calmly outperforms a better one that makes you panic-sell. **A practical middle path**: split it over three to six months, in equal amounts, on fixed dates. Long enough to reduce the sting of bad timing, short enough that you're not sitting in cash for years. Commit to the schedule in advance and don't deviate based on headlines — the failure mode of averaging in is stopping halfway because the market fell, which is exactly backwards. **Questions that should come first**, regardless of the answer: 1. Is your emergency fund complete? If not, that comes before investing any of it. 2. Do you have high-interest debt? Paying it off is a guaranteed return. 3. Will you need this money within five years? If yes, it shouldn't be in equities at all. **On 'what if it's a market peak'** — nobody can tell, including professionals. Markets spend a large proportion of time near all-time highs, because that's what an upward-trending series looks like. 'It's at a high' has been true for most of history and has almost no predictive value. If your horizon is genuinely ten-plus years, entry timing matters far less than staying invested.