If you plan to use CPF to invest in T Bills, read this before
proceeding.

The latest 6 months T Bills interest rates have fallen below 3%. It closed at
2.97%.

While the interest is higher than CPF ordinary account of 2.5%, it may not be
wise to use the funds to invest in T Bills as CPF balances used for interest
are affected by transactions in your account. 

Example

Withdrawals in this month will not earn interest from the month onwards.
Likewise, contributions received this month will only earn interest the next
month.

So potentially, you will lost 2 months of interest. 
Net loss of income = 2.5%/12*2 = 0.41%
Net Interest from  6 months T Bills = 2.97%/2 = 1.485%
Net return = 1.075% or approximately 2.15% per year

At the rate of 2.15%, it is less than the 2.5% guaranteed by CPF. Thus it DOES
NOT make any sense to use funds from an Ordinary Account to invest in 6 Months
T Bills. In fact, any rates below 3.3% for 6 months would make the switch to T
bills a potential financial loss.

At this rate, it will be better to keep your funds in CPF instead.

For more information on T Bills, here is a
Guide to investment in T Bills

DisclaimerThis post is for information only. It is not an invitation to investment.
Please seek investment advice from your financial consultants for your
investment needs.