我十二月top up 只是想免税。

要想多拿到利息的话可以一月top up

cpf 计算。利息跟银行不一样，它是按一个月最低的数字算利息的。比如你账号有10万，你一月一号存一万，一月份的利息是按照10万算的

Assuming you want to top-up $37,740 under the CPF Voluntary Contribution Scheme, the best time to top-up is at the end of the month since topping up at the beginning of the month will not earn any extra interest as interest is calculated based on the lowest balance for that month. Of course, in practice, you do not want to top-up on exactly on the last day of the month because you need to take into consideration of the turnaround time required for the computers and the cloud to sync and to run their batch processes at night - you could end up topping up on the 1st of the following month which is the worst-case scenario.