If you have not set aside your Full Retirement Sum (FRS) and have started your monthly payouts, your OA savings will be automatically transferred to your RA, up to your FRS. You will receive a notification before the transfer.
For example: Jane is born in 1960 and the principal amount in her RA is $148,000, which is below her FRS of $161,000. As she has started her monthly payouts, assuming she has $20,000 in her OA, $13,000 will be automatically transferred to her RA to set aside her FRS and increase her CPF LIFE monthly payouts. The remaining $7,000 will remain in her OA and she can choose to transfer it to her RA to increase her CPF LIFE payouts further or to withdraw anytime.