You will be able to explain why the timing of a top-up affects the interest it earns.
Linda, 52, keeps her CPF top-up money in a fixed deposit all year and transfers it to her Special Account on the last working day of December, every year, like clockwork. She says it's for the tax relief. Her daughter worked out that the same money, moved in January, would have earned her most of a year's extra CPF interest, and the tax relief would have been exactly the same.
Timing doesn't change whether a top-up is a good idea. It changes how much the top-up earns in its first year, and that difference repeats for every year you top up.
Lesson 1.2, How CPF interest is calculated and credited, explained that CPF works out interest each month on the lowest balance in that month. Money added during a month doesn't raise that month's lowest balance, so it starts earning from the following month.
For a top-up, that gives a simple rule. A top-up that lands in January earns interest from February to December, which is eleven months. One that lands in June earns for six months. One that lands in December earns nothing for that year and starts earning in January.
Here is the size of it, with made-up figures. Linda tops up S$5,000. At an example rate of 5% a year, which is not the current CPF rate, a January top-up earns S$5,000 times 5% times 11 divided by 12 in its first year, which is about S$229.17. A December top-up earns nothing in its first year. After that, both earn the same rate on the same S$5,000, but the January version is ahead by its first year's interest, and that interest compounds too. After ten years, the January top-up has grown to about S$8,112.15 and the December one to about S$7,756.64, a gap of about S$355.51.
That isn't life-changing on one top-up. Repeated every year for twenty years, it adds up to a meaningful amount, and the cost of getting it is only moving the date.
The tax relief is the usual reason given, and it is based on a misunderstanding. Relief is given for top-ups made in a calendar year, as long as the money arrives by 31 December. A top-up in January and one in December of the same year get the same relief, claimed in the same tax assessment the following year. Waiting until December doesn't add any relief. It only loses interest.
There are better reasons to wait. Many people don't have the cash until their bonus arrives, or they want to keep it in their buffer until the year is nearly over and they know nothing went wrong. Some want to see their final income for the year before deciding how much relief they can use, because reliefs above the yearly cap save nothing, as lesson 3.2, Cash top-ups for yourself and your family, mentioned. Those are real trade-offs between interest and cash flow.
There is one timing point almost everyone gets wrong. Compare a top-up on the last working day of December with one in the first week of January.
The December top-up qualifies for that year's relief, and because it is already in the account on 1 January, it earns interest from January onwards. The January top-up earns only from February, and its relief counts for the following year. If you were going to top up around the turn of the year anyway, late December beats early January on both counts. Leave a few days for the payment to be processed, and check the CPF Board's guidance on cut-off dates for each payment method.
You can top up the whole amount in January, if the cash is ready and your buffer stays intact without it. You get the most interest.
You can spread it monthly, for example by moving a twelfth of the yearly amount each month. Your cash flow stays even, and you earn roughly half of what a January lump sum would. On Linda's S$5,000, monthly top-ups would earn about S$114.58 in the first year, against S$229.17 for January and nothing for December.
You can top up once in late December, when you know your income and bonus for the year. You get the least interest in year one but the most certainty.
None of these is wrong. Linda kept her December date, because her fixed deposit pays her some interest in the meantime and she likes being sure her buffer is untouched. But she now moves the money in the third week of December rather than on the 31st.
Decide whether interest or cash flow matters more to you this year, then pick a month. Before you do, put a number on the trade by working out what a top-up made in January would earn compared with the same top-up in December, using the current SA rate from cpf.gov.sg.
Estimate the interest difference between a top-up made in January and one made in December, using the current SA rate.
Junxiong-WFG Organisation is an authorised representative of AIA Financial Advisers Private Limited (Reg. No. 201715016G).