Investing · South Africa
Should you invest a lump sum now or phase it into the market?
Investing sooner gives suitable long-term capital more time in the chosen portfolio. Phasing spreads the entry dates and can soften an early fall, but it can also leave you behind when prices rise. Neither method protects you from losses once all the money is invested. The first decision is therefore how much belongs in that portfolio; the entry schedule comes second.
This matters after an inheritance, business sale or other large receipt. The amount arriving in your bank account may include money needed for tax, spending or replacing income. Setting that money aside is a funding decision. It should not be confused with waiting for a better market price.
In this article
Compare two ways of investing the same money
Consider an invented R1.2 million, available after reserves and known liabilities. One approach invests everything at the start of month one. The other invests R400,000 at the start of months one and two, then the remaining cash at the start of month three. Both end up in the same investment.
Assume waiting cash earns 0.5% a month before personal tax. That is an illustration, not a bank quotation. After the first purchase, R800,000 earns R4,000. After the second purchase, the remaining R404,000 earns R2,020. The last purchase is therefore R406,020. A comparison that forgets the waiting cash or its interest is incomplete.
The table measures the whole amount after twelve months. Investment returns are assumed after investment costs but before personal tax; dealing charges are excluded. The deliberately simple paths isolate entry timing. Returns after month three are set to zero in every path. They are not forecasts, and no likelihood is assigned to them.
| Invented investment path | Invest all at once | Three purchases |
|---|---|---|
| +10%, +10%, then no change | R1,452,000 | R1,330,020 |
| −10%, −10%, then no change | R972,000 | R1,090,020 |
| No change for two months, then −30% | R840,000 | R844,214 |
In the rising path, delaying costs R121,980. In the early falling path, phasing finishes R118,020 ahead. Both results follow from when money was exposed to those particular returns. A favourable example does not establish that one entry method will win next time.
The third row is especially useful. The fall happens after both approaches are fully invested. Phasing retains only a small advantage from earlier cash interest; both suffer a substantial loss. If that outcome would make an essential payment impossible, changing the entry dates has not solved the underlying problem.
What the historical evidence can tell you
Vanguard's February 2023 study found that immediate investment beat three equal monthly purchases in 68% of its historical comparison. That case used MSCI World returns for 1976–2022, a 100% equity allocation, a one-year measurement period and no interest on the waiting cash. The study also discusses why an investor strongly averse to losses might prefer phasing to leaving the entire amount in cash. Vanguard research, pages 2–3 and 6–8.
A historical frequency is not a 68% probability offered to a South African investor today. Your asset mix, currency, cash yield, costs, tax and dates may differ. Nor does “wins more often” answer how much an early loss would hurt, or whether you would abandon the investment afterwards.
A schedule needs an end date
Phasing is most useful as a defined implementation choice, not an invitation to make another market prediction every month. Write down the amount, the investment, the purchase dates, where waiting cash will sit and when the process finishes. Identify who will place the instructions. Otherwise “three months” can become “until the news improves”.
Test the schedule against both regrets. If markets fall after the first purchase, would you cancel the next one? If markets rise, would you discard the schedule and invest everything immediately? Neither answer makes you foolish. It reveals that the proposed rule may not be one you will actually follow.
There are legitimate reasons to reconsider: a changed tax bill, a newly confirmed expense or evidence that the intended investment is unsuitable. Those change the available money or its purpose. A price move alone changes the experience of the schedule without necessarily changing the reason for having it.
Do not use entry timing to avoid choosing an allocation
Investing gradually into a portfolio you cannot afford to hold through a fall postpones the problem. Compare the eventual exposure with your obligations and available reserves. An immediately funded, less aggressive allocation and a phased, more aggressive allocation remain different investments after the entry period ends.
For offshore purchases, there is another distinction: converting currency and buying investments are separate actions. Converting all the rands first and investing over three months differs from converting and investing each instalment. Record the currency holding the waiting cash and include actual conversion charges before attributing a result to the entry strategy.
The useful question is not which method lets you feel certain. Neither does. It is whether the amount, eventual portfolio and implementation rule can survive the outcomes that would matter to your household. Judge the choice against that purpose, rather than the lowest price visible afterwards.
Before choosing purchase dates, use the market-crash question to examine whether the eventual portfolio and your spending commitments fit together.
General education for South African readers. Examples are invented calculations, not client outcomes or personal recommendations. Actual charges, tax and cash needs require a separate assessment. The historical research is dated February 2023; the rand examples are not replications of its sample.
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