The arithmetic of $4,600

$4,600 a month is the Retirement Account payout — a scheduled drawdown of a single pot of money. $30,000 a year is interest thrown off by a separate balance of more than $1 million sitting in her Ordinary and MediSave Accounts, which is not being drawn down at all. Together they make the $85,000 a year, or roughly $7,000 a month, of total CPF income.

The distinction matters. The payout is capital being consumed on a schedule. The interest is yield on capital being preserved. One has an end date; the other does not. Most of the commentary around cases like this treats them as the same thing, which is how a reader ends up with the wrong target.

The headline 4% is a floor, not the whole rate. On top of it the Government pays extra interest on combined balances: below 55, 1% on the first $60,000; from 55, 2% on the first $30,000 and 1% on the next $30,000. For a member past 55 the first $30,000 in the Retirement Account therefore earns 6%, the next $30,000 earns 5%, and everything beyond earns 4%.

In cash terms the tiered bonus is worth a fixed $900 a year once the RA exceeds $60,000. That is trivial against a $600,000 balance — but it was not trivial in 2010, when it was worth 0.49% on top of the base rate. The tiers front-load the return, which rewards getting money in early rather than getting a lot of money in later.

From 55, a member may top up the Retirement Account to the current year's ceiling. Before 2016 that ceiling was the prevailing Minimum Sum. From 2016 it became the Enhanced Retirement Sum, set at 1.5 times the Full Retirement Sum. From 2025 it was reset to four times the Basic Retirement Sum — a step change that raised it by 38% in a single January.

The critical detail is what counts against the ceiling. The top-up limit is measured against the principal you have set aside, not the balance you hold. Interest already credited does not consume your headroom. So each January the ceiling moves up, the member tops up the increment, and the interest earned on everything below simply accumulates on top, permanently outside the cap.

Over sixteen years this produces the divergence in the chart above: a principal line that tracks the ceiling exactly, and a balance that ends 46% higher than the ceiling it was never allowed to exceed.

Under the Retirement Sum Scheme, the monthly payout is calculated to last up to 20 years from the payout eligibility age of 65 — that is, to about 85 — with extra interest used to stretch payouts as far as 90. Starting at 70 leaves a 15-year horizon on that basis. The required capital is a standard present-value calculation.

On your 55th birthday CPF opens a Retirement Account and sweeps money into it — Special Account first, then Ordinary Account — until the Full Retirement Sum is met. Anything above that stays in the OA and is freely withdrawable, in as many separate withdrawals as you like. If your balances fall short of the FRS you can still take out $5,000 unconditionally.

Then comes the decision that quietly costs more than any other in the system. If you own property with a lease running to at least age 95, you may pledge it, set aside only the Basic Retirement Sum in cash, and withdraw the difference. In 2026 that frees $110,200 on the spot.

Members born before 1958 default to the Retirement Sum Scheme; those born from 1958 with at least $60,000 in the RA go into CPF LIFE, the national annuity. On an identical $621,900 balance the two schemes behave very differently. The drawdown pays about $4,578 a month and ends. The annuity pays about $3,579 a month — 78% as much — and never ends.

Cumulative payouts cross at about age 89. Before that the drawdown is ahead; after it, the annuity pulls away without limit. That is the trade the newer cohorts have been moved into: a lower monthly cheque in exchange for removing the possibility of outliving the money. On current Singapore longevity, a large share of 70-year-olds will reach the crossover.

Anyone reaching 65 with at least $60,000 in the Retirement Account is included in CPF LIFE automatically. The Standard Plan is the default, and most members never actively choose. The three plans differ in how much of the RA is converted into annuity premium, and in whether the monthly figure stays flat or climbs.

Take a member turning 55 in 2026 who sets aside the ERS of $440,800 and then tops up the increment every January to age 70. The ceiling is published through 2027 and projected at 3.5% a year thereafter. The result below is calibrated so that the no-top-up case reproduces the CPF Board's own published estimate of $4,580 a month at 70.

The intuition that the last dollar into the Retirement Account is worth less than the first is widespread, and the average figures appear to confirm it: fifty thousand dollars set aside at 55 buys $13.49 of monthly payout per thousand, while the full Enhanced Retirement Sum buys only $10.39. That looks like a clear case of diminishing returns.

It is not. Compute the marginal rate — what each additional thousand buys, rather than what the whole stack averages — and it is flat at essentially ten dollars all the way up.

Which raises the sharper question: if you intend to top up every January anyway, how much does the opening set-aside matter at all? The ladder tops up to the prevailing ceiling regardless of where you started, and unused headroom carries forward. All three paths below therefore converge on identical principal.

Irreversibility. Top-ups to the Retirement Account cannot be reversed, withdrawn or redirected. The Ministry of Manpower confirmed in January 2026 that CPF LIFE members cannot opt out of having top-ups streamed into the annuity. Money that goes in is committed for the rest of your life.

Liquidity. $426,000 locked at 4% is $426,000 that cannot meet a medical bill, a family emergency, or a business opportunity. The payout is excellent; the optionality forgone is real and does not appear anywhere in the return calculation.

Bequest asymmetry. Under the drawdown scheme, unpaid balances including interest pass to beneficiaries. Under CPF LIFE, beneficiaries receive the premium paid less payouts already made — not the interest, which is pooled to fund other members' longevity. A member who dies early has, in effect, subsidised the ones who live long. That is what the insurance is.

Inflation. The Standard Plan pays a level nominal amount. At 2.5% inflation a payout starting in 2041 loses a third of its purchasing power by 2058. The Escalating Plan starts about 20% lower and rises 2% a year; whether that trade is worth taking is a longevity bet, not a maths question.

Rate risk. The 4% floor on SA, MediSave and RA monies is extended by the Government one year at a time — currently to 31 December 2026. It is not statutory in perpetuity. Every projection here, including the Board's own, assumes it holds.

Opportunity cost. 4% guaranteed is an extraordinary risk-free rate. It is also a long way below long-run equity returns, and the ceiling means you cannot use CPF to compound a large sum anyway. The new life-cycle investment scheme arriving in the first half of 2028 will offer a middle path, with two to three providers, capped fees and a glide path that liquidates into the RA before the payout age.